The
HAMMOND
Organ Manual
for the
SERVICE ENGINEER
Models:
A
A-100, AB,
BC, BCV, BV,
B2, B3, C, CV, C2,
C2-G, C3, D, DV, D-100,
E, G, GV, RT, RT2, RT3
|hiii|
This manual is intended for FREE
distribution
Foreword
to the
201 6 Edition
This new edition exists to provide an alternative to the poor quality publications of
Hammond's own H000-000495 master service manual that surfaced in various guises
during the late 70s - early 80s; as well as the even worse quality of the scanned material
found on the Internet as of this writing.
Hammond created the H000-000495 by making copies of copies, shrinking down
diagrams, and resetting certain paragraphs (often sloppily) to accommodate the inclusion
of models that were developed after the initial manuals had been written years before.
Every attempt has been made to be as accurate and authentic as possible to the original
manuals in terms of content and layout. Pictures have been replaced when possible (or
necessary) & sections clarified when needed. The format of this new, inclusive manual
follows more closely layout of the older versions from the 50s adding in the newer models
in the appropriate places. References to the Model BA were intentionally removed due to
lack of documentation of the "player" section. Also removed were any references to
buying new parts, as well as the Parts List itself due to their obsolescence.
The diagrams have been scanned at a 600dpi resolution from the oldest sources that
could be found. These older sources were typically fold out diagrams 1 7"x1 1 " in size.
While they have been reformatted to 14"x8" to maintain continuity within the PDF format,
the high resolution of the scans allows for very clear zooming. Also included are some
diagrams and subjects that existed in the 40s & 50s literature, but were omitted from the
later 000495 manual.
This endeavor was done for the love of Hammond Organs and to assist in their
preservation. It is NOT meant to offer REVISIONS in the diagrams and schematics that
differ from Hammond originals. Hammond was very lax in offering revisions and often
they were the results of individual technicians based on their experience.
The manual is intended to be distributed FREE of COST.
Thanks goes out to the Audio Playground Synthesizer Museum for scanning the
Introduction section and getting the ball rolling.
Enjoy...
Joe Luca
May, 2016
THE HAMMOND ORGAN
MANUAL
FOR THE SERVICE ENGINEER
HAMMOND ORGAN COMPANY
North Western Avenue - Chicago
Diversey Ave - Chicago
North 25 th Avenue - Melrose Park
Copenhagen Court - Franklin Park
Illinois
USA
FOREWORD
The Hammond Organ is a product of a company which
enjoys a world-wide reputation as a manufacturer
of precision electrical devices. The manufacturing
facilities devoted to the production of the
organ are the finest in existence for this type
of work. Thus, a background of specialized engineering
experience plus modern fabricating
methods are behind the Hammond Organ guarantee.
The Hammond Organ Company, in its guarantee, gives
the customer assurance that adequate facilities
will be available at all times to service the
instrument. This manual is designed to supply the
service technician with all information essential
to his rendition of this service. It is designed
to serve three purposes: first, to help make effective
installations; second, as a guide in proper
maintenance; and third, to provide instructions
on making repairs if they become necessary.
HAMMOND ORGAN COMPANY
North Western Avenue - Chicago
Diversey Ave - Chicago
North 25 th Avenue - Melrose Park
Copenhagen Court - Franklin Park
Illinois
USA
SAFETY NOTICE
Great care has been taken In the design and manufacture of this product to assure that no
shock hazard exists on any exposed metal parts. Internal service operations can expose the
technician to hazardous line voltages and accidentally cause these voltages to appear on
exposed metal parts during repair or reassembly of product components. To prevent this, work
on these products should only be performed by those who are thoroughly familiar with the
precautions necessary when working on this type of equipment.
To protect the user, It is required that all enclosure parts and safety Interlocks be restored to
their original condition and the following tests be performed before returning the product to
the owner after any service operation.
Plug the AC line cord directly Into a line voltage AC receptacle (do not use an Isolation
transformer for this test) and turn the product on. Connect the network (as shown below) In
series with all exposed metal parts and a known earth ground such as a water pipe or conduit.
Use an AC VOM of 5,000 ohms per volt or higher sensitivity to measure the voltage drop across
the network. Move the network connection to each exposed metal part (metal chassis, screw
heeds, knobs and control shafts, escutcheon, etc.) end measure the voltage drop across the
network. Reverse the line plug and repeat the measurements. Any reading of 4 volts RMS or
more Is excessive and Indicates a potential shock hazard which must be. corrected before
returning the product to the user.
TO EXPOSED METAL PARTS
THE HAMMOND ORGAN
- 1 -
INTRODUCTORY SECTION
HAMMOND ORGAN COMPANY
North Western Avenue - Chicago
Diversey Ave - Chicago
North 25 th Avenue - Melrose Park
Copenhagen Court - Franklin Park
Illinois
USA
SPECIFICATIONS MODEL A - AB
IN PRODUCTION:
SELLING PRICE:
DIMENSIONS:
FINISH:
MANUALS :
PEDAL
KEYBOARD :
TONAL
CONTROLS :
9 p
EXPRESSION:
FEATURES:
: June 1935 to October 1938.
: $1,193.00. With Model A-20 Tone Cabinet $1,250.00.
Closed: 48-1/2" wide, 37-5/8" high, 24" deep.
Open: 48-1/2" wide, 47" high, 38-1/2" deep.
American walnut.
Swell and Great, 61 playing keys each.
25-note, radiating; detachable,
reset keys and 2 sets of 9 adjustable harmonic drawbars
for each manual; 2 adjustable drawbars (16' and 8') for
pedals .
One expression pedal controlling Swell, Great, and Pedals
One tone generator. One adjustable tremulant affecting
both manuals and pedals equally.
AC INPUT:
WEIGHT:
Approx. 30 watts, plus wattage required by Tone Cabinets.
As illustrated, approx. 359 pounds.
Serial No. 2501 and above used larger woodwork case designated as AB . See B
series for case dimensions and weight.
3
SPECIFICATIONS HOME MODELS BC, BV, BCV, B-2, AND B-3
DIMENSIONS:
MODEL AB:
MODEL BC:
IN PRODUCTION.
SELLING PRICE:
Closed, without pedal keyboard 48-3/8" wide, 28-3/4" deep,
38-3/8" high. Open, with pedal keyboard and bench: 48-3/8"
wide, 49-1/2" deep, 46" high.
Same as Model A but enclosed in larger woodwork. One tone
generator, one adjustable tremulant affecting both manuals
and pedals equally. Also see Model A for price and pro-
duction dates.
Same as Model AB but with one additional generator and
appropriate switching to create chorus effect.
December 1936 to November 1942.
$1,342 . 00 - Walnut .
MODEL BV : Same as Model B but equipped with Hammond Vibrato providing
three degrees of true Vibrato and "off" position, effective
simultaneously on both manuals, together with Vibrato Chorus
usable in three different degrees and "off".
IN PRODUCTION: April 1946 to December 1949.
SELLING PRICE: $1,881.00 - Walnut.
MODEL BCV : Same as Model BC but has Hammond Vibrato and Vibrato
Chorus .
Noneproduced. Converted by Vibrato Kit added after 1945.
Kit price - $275.00.
MODEL B-2: Same as Model BV but with controls which provide Vibrato
on either or both manuals. Also additional control for
"normal" or "soft" overall volume.
IN PRODUCTION: December 1949 to December 1954.
SELLING PRICE: $2,288.00 - Walnut
4
SPECIFICATIONS HOME MODELS BC, BV, BCV, B-2, AND B-3 (Continued)
MODEL B-3: Same as Model B-2 but with Hammond Percussion feature.
IN PRODUCTION: January 1955 to
SELLING PRICE: $2,745.00 - Walnut. $2,835.00 - Cherry.
MANUALS: Swell and Great, 61 playing keys each.
PEDAL
KEYBOARD: 25-note radiating, detachable.
TONAL 9 preset keys and 2 sets of 9 adjustable harmonic drawbars
CONTROLS: for each manual. 2 adjustable drawbars (16' and 8') for
pedals .
EXPRESSION: One expression pedal controlling Swell, Great and Pedals.
AC INPUT: Approximately 30 to 50 watts, plus wattage required by
Tone Cabinets.
WEIGHT: As illustrated, approximately 425 lbs.
5
SPECIFICATIONS CHURCH MODELS C, CV, C-2, C-3, D AND DV
DIMENSIONS:
Closed, without pedal keyboard: 48-3/4" wide, 29" deep,
38-3/4" high. Open, and with pedal keyboard and bench:
48-3/4" wide, 47" deep, 46" high.
MODEL C: Same as Model AB but with different style woodwork. One
IN PRODUCTION:
tone generator, one adjustable tremulant affecting both
manuals and pedals equally.
September 1939 to June 1942.
SELLING PRICE:
$1,193.00 - Walnut .
MODEL CV : Same as Model C but equipped with Hammond Vibrato,
IN PRODUCTION:
including Vibrato Chorus .
September 1945 to December 1949.
SELLING PRICE:
$1,782.00 - Walnut.
MODEL C-2: Same as Model CV but with controls which provide Vibrato
on either or both manuals. Also additional control for
IN PRODUCTION:
"normal" or "soft" overall volume.
December 1949 to December 1954.
SELLING PRICE:
$2,178.00 - Walnut.
MODEL C-3: Same as Model C-2 but with Hammond Percussion feature.
IN PRODUCTION:
January 1955 to
SELLING PRICE:
$2,545.00 - Walnut. $2,630.00 - Oak.
Later version in both finishes less quatrefoil.
7
SPECIFICATIONS CHURCH MODELS C, CV, C-2, C-3,D AND DV (Continued)
MODEL D: Same as Model C but with one additional tone generator and
appropriate switching to create chorus effect. Similar to
Model BC.
IN PRODUCTION: June 1939 to November 1942.
SELLING PRICE: $1,342.00 - Walnut.
MODEL DV : Same as Model D but with Hammond Vibrato, including
Vibrato Chorus. See BCV.
None produced. Kit added in field.
MANUALS: Swell and Great, 61 playing keys "ch.
PEDAL
KEYBOARD: 25-note, radiating, detachable.
TONAL 9 preset keys and 2 sets of 9 adjustable harmonic drawbars
CONTROLS: for each manual; 2 adjustable drawbars (16' and 8') for
pedals .
EXPRESSION: One expression pedal controlling Swell, Great, and Pedals.
AC INPUT: Approximately 40 to 60 watts, plus wattage required by
Tone Cabinets.
WEIGHT: As illustrated, approximately 450 lbs.
8
SPECIFICATIONS CONCERT MODEL E
DIMENSIONS: Closed, without pedal keyboard: 57" wide, 40" high, 29"
deep. Open, and with pedal keyboard: 57" wide, 46-7/8"
high, 47-5/8" deep.
IN PRODUCTION: July 1937 to July 1942.
SELLING PRICE: $1,980.00.
FINISH: American Walnut.
MANUALS: Swell and Great, 61 playing keys each.
PEDAL 32-note, concave, radiating, detachable, built to AGO
KEYBOARD: specifications.
TONAL 9
CONTROLS :
EXPRESSION:
FEATURES :
preset buttons and 2 sets of 9 adjustable harmonic draw-
bars for each manual; for pedals - 4 numbered and labeled
toe pistons 2 adjustable drawbars (16' and 8') and Great
to Pedal 8' coupler.
2 expression pedals, one for Swell and one for Great and
Pedals. Visual position indicators of sliding rod type.
Separate adjustable tremulants for Swell and Great
Manuals . St andard Main and Chorus generator units; on and
off switch for Chorus.
AC INPUT: Approximately 50 watts, plus wattage required by Tone Cabinets.
WEIGHT: As illustrated, approximately 579 lbs.
9
U.S. GOVERNMENT PURCHASED EQUIPMENT
MODEL G CONSOLE AND TONE CABINET
The Model G consoles and tone cabinets were built for the Government, and
now will be found in use throughout the United States and foreign countries
in chapels of all services. Officers Clubs, or recreation service build-
ings .
The console is identical to the Model D except for the decorative woodwork
and provision for detachable handles.
The tone cabinet (Model G-40) contains two amplifiers and four speakers
mounted in a horizontal row and is electrically similar to Model B-40 tone
cabinet, but has a reverberation control unit.
Produced from June 1941 to November 1944.
MODEL C-2G, C-3G CONSOLES AND HR-40G
These consoles are identical in appearance to the C-2 and C-3 except that a
monitor speaker is located on the lower left hand side.
The preamplifier in the C-2G is designed to operate the monitor speaker. In
the C-3G the preamplifier is the same as in the C-3. A small auxiliary
amplifier drives the monitor speaker. In both Models, B+ voltage from the
tone cabinet is required to make the monitor speaker operative.
The HR-40G is identical to the HR-40 except that it is equipped with a
standard 6 conductor cable which must be used in conjunction with the C-2G
console .
C-2G in production June 1952 to March 1953.
C-3G in production January 1955 to ?
10
SPECIFICATIONS CONCERT MODELS RT, RT-2, AND RT-3
DIMENSIONS: Closed, without pedal keyboard: 57" wide, 40" high, 29"
deep. Open, and with pedal keyboard: 57" wide, 46-7/8"
high, 47-5/8" deep.
CONCERT Equipped with Hammond Vibrato providing three degrees of
MODEL RT : true Vibrato and an "off" position, effective simultane-
ously on both manuals, together with Vibrato Chorus usable
in three different degrees and "off".
IN PRODUCTION: July 1949 to September 1949.
SELLING PRICE: $2,475.00 - Walnut.
CONCERT Same as Model RT but with controls which provide Vibrato
MODEL RT-2: on either or both manuals, also additional control for
"normal" or "soft" overall volume.
IN PRODUCTION: November 1949 to January 1955.
SELLING PRICE: $2,970.00 - Walnut.
CONCERT
MODEL RT-3: Same as Model RT-2 but with Hammond Percussion feature.
IN PRODUCTION: January 1955 to
SELLING PRICE: $3,450.00 - Walnut . $3, 555 . 00 - Oak.
11
SPECIFICATIONS CONCERT MODELS RT, RT-2, AND RT-3 (Continued)
MANUALS: Swell and Great, 61 playing keys each.
PEDAL 32-note, concave, radiating, detachable, built to AGO
KEYBOARD: specifications.
PEDAL SOLOHas pedal solo system with separate volume control,
SYSTEM: providing following solo effects; 32-foot Bourdon,
32-foot Bombarde, 16-foot Solo, 8-foot Solo, 4-foot
Solo, 2 and 1-foot Solo. Also tablets for Mute Control
and Pedal Solo On.
TONAL 9 preset keys and 2 sets of 9 adjustable harmonic drawbars
CONTROLS: for each manual; for pedals, two adjustable drawbars
(16 ' and 8 ' ) .
EXPRESSION: One expression pedal, controlling Swell, Great, and Pedals.
AC INPUT: Approximately 110 to 130 watts, plus wattage required by
Tone Cabinets.
WEIGHT: As illustrated, approximately 525 lbs.
12
MODEL A-20 TONE CABINET
SPECIFICATIONS
IN PRODUCTION:
October 1935 to July 1939.
SELLING PRICE:
$165.00.
DIMENSIONS:
27" wide, 30" high, 15" deep.
FINISH:
American Walnut.
WEIGHT:
113 pounds.
OUTPUT :
20 watts - 1 amplifier, 2 - 12" speakers.
AC INPUT:
Approximately 180 watts.
This small decorative tone cabinet is used for homes, mortuaries, and small
churches, seating not over 100 persons, where a limited amount of power is
required.
TC-1
MODEL A-40 TONE CABINET
SPECIFICATIONS
IN PRODUCTION: October 1935 to October 1947.
SELLING PRICE: $225.00.
DIMENSIONS: 26-1/2" wide, 28" high, 19" deep.
FINISH:
WEIGHT :
OUTPUT :
AC INPUT:
Black lacquer.
155 pounds.
40 watts - 2 amplifiers, 4 - 12" speakers.
Approximately 360 watts.
A non-decorative, double-strength cabinet, designed for use
four or more, in large installations where the cabinets are
in banks of
concealed .
TC-2
MODEL B-40 TONE CABINET
SPECIFICATIONS
IN PRODUCTION: November 1936 to December 1947.
SELLING PRICE:
DIMENSIONS:
FINISH:
WEIGHT:
OUTPUT :
AC INPUT:
$247.00.
36" wide, 36"
Walnut stain.
225 pounds.
40 watts - 2
Approximately
high, 28-1/2"
amplifiers, 4
360 watts.
deep .
- 12 " speakers .
A semi-decorative, double-strength cabinet designed for use individual]
in groups. The B-40 is found desirable for many churches and for large
installations, for it may be used appropriately in almost any setting.
or
TC-3
MODEL C-20, CX-20, AND CXR-20 TONE CABINET
SPECIFICATIONS
MODEL C-20:
IN PRODUCTION: October, 1937 to March, 1942.
SELLING PRICE: $270.00
MODEL CR-20: Equipped with Reverberation Unit.
IN PRODUCTION: 1939 - 1942.
SELLING PRICE: $407.00
MODEL CX-20: Equipped with rotor tremulant. See Page TC-7 for picture
of this feature.
IN PRODUCTION: January, 1939 to March, 1942.
SELLING PRICE: $335.00
MODEL CXR-20: Equipped with rotor tremulant and reverberation unit.
IN PRODUCTION: November, 1939 to March, 1942.
SELLING PRICE: $473.00
TC-4
DIMENSIONS:
2 9" wide, 53" high, 18-1 j4" deep.
FINISH:
WEIGHT:
OUTPUT :
AC INPUT:
Matched American butt walnut and antique brass hardware.
153 lbs.
20 watts, 1 amplifier, 2 - 12" speakers.
Approximately 200 watts.
TC-5
MODEL C-40 TONE CABINET
SPECIFICATIONS
December 1937.
IN PRODUCTION:
June 1936 to
SELLING PRICE:
$330 . 00 .
DIMENSIONS:
38" wide, 71"
FINISH:
Walnut stain.
WEIGHT:
313 pounds.
OUTPUT :
40 watts - 2
AC INPUT:
Approximately
high, 27-1/2" deep.
amplifiers and 4 - 12"
360 watts.
speakers .
The C-40 cabinet has a wide variety of applications. It is especially
adapted for use in enclosures where the indirect projection of sound is
desirable. Very often the ceiling and floor are the only "live" or reflect-
ing surfaces and this type cabinet makes use of these.
The C-40 cabinet is used individually or in groups of two or more.
TC-6
MODEL .
D-20 TONE CABINET MODEL DXR-20 TONE CABINET
SPECIFICATIONS
MODEL D-20: Tonally identical with Model C-20, the D-20 fills a need
for an inexpensive cabinet for use in a wide variety of
installations where decorative qualities are a secondary
consideration .
IN PRODUCTION: October 1937 to March 1952.
SELLING PRICE: $181.00.
MODEL DX-20: Equipped with rotor tremulant.
IN PRODUCTION: October 1938 to June 1942.
SELLING PRICE: $249.00
MODEL DR-20: Equipped with reverberation unit.
IN PRODUCTION: August 1939 to March 1952.
SELLING PRICE: $319.00.
MODEL DXR-20: Equipped with rotor tremulant and reverberation unit.
IN PRODUCTION: April 1939 to June 1945.
SELLING PRICE: $385.00.
DIMENSIONS:
FINISH:
WEIGHT:
OUTPUT :
AC INPUT:
28" wide, 56" high, 16-3/4" deep.
Face and sides of American walnut.
149 pounds - D-20; 171 pounds - DR-20; 178
20 watts - 1 amplifier, 2 - 12"speakers.
Approximately 200 watts.
pounds
DXR-20 .
TC-7
MODEL ER-20 TONE CABINET
SPECIFICATIONS
IN PRODUCTION: March 1947 to December 1950.
SELLING PRICE: $462.00.
DIMENSIONS: 31" wide, 38-3/4" high, 18" deep.
FINISH: Walnut.
WEIGHT: 144 pounds.
OUTPUT: 20 watts - 1 amplifier, 2 - 12" speakers.
AC INPUT: Approximately 200 watts.
The ER-20 tone cabinet is electrically equivalent to the DR-20 tone
cabinet. However, the woodwork is designed for use in homes where a
artistic cabinet is preferred.
more
TC-8
MODEL F-40 AND FR-40 TONE CABINET
IN PRODUCTION: January 1948 to December 1957.
SELLING PRICE: F-40 - $406.00. FR-40 - $560.00.
DIMENSIONS:
FINISH:
WEIGHT:
OUTPUT :
AC INPUT:
32-15/16" wide; 39-3/16" high; 28-3/8" deep.
Walnut stain.
F-40 - 208 lbs. FR-40 - 228 lbs.
40 watts - 2 amplifiers, 4-12" speakers.
Approximately 300 watts.
The F-40 replaces the B-40 tone cabinet. Dimensions of the woodwork have
been altered so that a reverberation unit may be accommodated . With the
addition of the reverberation unit it is designated as FR-40.
TC-9
MODEL H-40, HR-40, K-40, AND KR-40 TONE CABINET
MODEL H-40 AND HR-40:
IN PRODUCTION: October 1948 to February 1960.
SELLING PRICE: H-40 - $517.00 - Walnut.
HR-40 - $585.00 - Walnut.
HR-40 - $605.00 - Oak.
DIMENSIONS: 33-1/8" wide; 48" high; 16-7/8" deep.
MODEL K-40 AND KR-40:
IN PRODUCTION: December 1957 to February 1960.
SELLING PRICE: K-40 - $427.00, KR-40 - $495,00.
DIMENSIONS: 32-1/2" wide; 48" high; 15-7/8" deep,
WEIGHT: K-40 and H-40 - 147 lbs.
KR-40 and HR-40 - 162 lbs.
AC INPUT:
OUTPUT :
H-40 Early Units - 234 watts. Later units - 175 watts.
HR-40 Early Units - 240 watts. Later units - 175 watts.
K-40 and KR-40 - 175 watts.
40 watts - 1 amplifier, 11 speakers; 2-12", 9-10".
The H series tone cabinets are designed for use in all types of installa-
tions; church, home, school and entertainment places. Their response is
non-direct ional , with the high frequencies projected vertically and the low
frequencies horizontally.
TC-10
MODEL H-40, HR-40, K-40, AND KR-40 TONE CABINET (Continued)
The K series tone cabinets are electrically and tonally similar to the H
series but are constructed in a utilitarian cabinet. Usually used in con-
cealed installations. The two treble speakers usually mounted on top can be
placed on the front baffle for use in chambers where vertical radiation
would be restricted.
The tone cabinet contains separate amplifier sections for treble and bass
response with cross-over point at 200 cycles.
Amplifiers are not interchangeable with amplifiers in other model tone cab-
inets .
The HR-40 and KR-40 have reverberation on treble section only. Reverberated
signal cannot be fed to another tone cabinet.
Earlier models of the H series tone cabinet were equipped with separate
treble and bass amplifier units. These amplifiers were later consolidated
in one unit .
For weight of earlier units add 31 pounds to above figures.
TC-11
MODEL JR-20 TONE CABINET
SPECIFICATIONS
IN PRODUCTION: March 1951 to February 1959,
SELLING PRICE: $452.00 - Walnut. $472.00 - Oak.
DIMENSIONS:
WEIGHT:
29-3/4" wide; 39-3/4" high; 15-7/8" deep,
120 pounds.
AC INPUT:
OUTPUT :
100 watts.
20 watts - 1 amplifier -T treble speaker - 12"
4 bass speakers - 10"
The JR-20 tone cabinet is ideal for the home, small church, mortuary and
entertainment places. Its response is non-direct ional with the highs pro-
jected vertically and the lows horizontally.
The amplifier is constructed with separate sections for bass and treble
response with a cross-over point at 200 cycles. A reverberation preamplifi-
er is also incorporated in the amplifier chassis and reverberation is
obtainable in three degrees on each channel, independent of each other. The
reverberation signal cannot be transferred to other tone cabinets.
TC-12
MODEL PR-20 FRONT
MODEL PR-20 REAR
SPECIFICATIONS
IN PRODUCTION:
: February 1959 to July 1963.
SELLING PRICE:
Walnut - $485.00
Oak - $505.00
Provincial - $505.00
DIMENSIONS:
31-1/2" wide; 37-1/2" high; 18" deep.
WEIGHT:
118 lbs.
AC INPUT:
185 watts.
OUTPUT :
20 watts.
Equipped with two 15" speakers for bass tones and two 12" speakers for the
treble tones. They provide three dimension amplification which creates a
beautiful reverberation effect in stereo. These cabinets feature the new
and improved Hammond Reverberation control for both bass and treble tones.
Convenient outside controls make it easy to change the degree of reverbera-
tion for each.
TC-13
MODEL P-40
MODEL Q-4 0
MODEL P-40:
IN PRODUCTION:
SELLING PRICE:
DIMENSIONS:
WEIGHT:
June 1959 to April 1963.
$540.00 - Walnut. $560.00 - Oak. $560.00 - Provincial.
31-1/2" wide; 37-1/2" high; 18" deep.
126 lbs.
MODEL Q-4 0 :
IN PRODUCTION: June 1959
SELLING PRICE: $465.00
DIMENSIONS: 31" wide; 36-5/8" high; 17-1/4" deep.
WEIGHT: 110 lbs.
AC INPUT: 175 watts.
OUTPUT: 55 watts E.I.A.
Equipped with a two channel amplifier, two 15" speakers and two 12" speak-
ers serving the bass and treble channels respectively. This tone cabinet in
conjunction with a Hammond tone cabinet with reverberation can add the
additional power required for larger installation at a minimum cost. Can
also be used alone where sufficient natural reverberation is evident.
The Q-40 is electrically similar to the P-40 but with utility type cabinet
is only used where appearance is not a consideration such as tone and
reverberation chambers.
The treble speakers are normally mounted in the top. In unusual installa-
tion where the ceiling is very low, or cabinets are stacked or radiation is
otherwise restricted, it is possible to move these speakers to the holes
provided in the front. The metal diffusers in front of the speakers must
also be moved and the wooden covers must be attached under the top to close
the holes.
TC-14
MODEL PR-40
MODEL QR-40
SPECIFICATIONS
MODEL PR-40:
IN PRODUCTION: February 1959
SELLING PRICE: $615.00 - Walnut
$645 .00 - Oak
$645 .00 - Cherry
DIMENSIONS: 31-1/2" wide; 37-1/2" high;
WEIGHT: 130 lbs.
18" deep.
MODEL QR-40:
IN PRODUCTION:
SELLING PRICE:
DIMENSIONS:
WEIGHT:
AC INPUT:
OUTPUT :
June 1959.
$535.00
31" wide; 36-5/8" high;
121 lbs.
220 watts
50 watts E . I . A.
17-1/4" deep.
Equipped with two 15" speakers for bass tones and two 12" speakers for the
treble tones. They provide three dimension amplification which creates a
beautiful reverberation effect in stereo. These cabinets feature the new
and improved Hammond Reverberation control for both bass and treble tones.
Convenient outside controls make it easy to change the degree of reverbera-
tion for each.
TC-15
MODEL PR-40 AND QR-40 SPECIFICATIONS (Continued)
The QR-40 is electrically similar to the PR-40 but with its utility type
cabinet is only used where appearance is not a consideration, such as in
tone and reverberation chambers.
The treble direct speaker is normally mounted in the top. In an unusual
installation where the ceiling is very low, or cabinets are stacked or
radiation is otherwise restricted, it is possible to move this speaker to
the hole provided in the front. The metal diffuser in front of the speaker
must also be moved, and the wooden cover must be attached under the top to
close the hole.
TC-16
SPECIFICATIONS A-100 SERIES
MODEL STYLE FINISH
IN PRODUCTION SELLING PRICE
A-100
A-100
A-101
A-101
A-101
A-102
A-102
A-105
A-105
A-122
A-143
Traditional
Traditional
Contemporary
Contemporary
Contemporary
Fr .Provincial
Fr .Provincial
Tudor Walnut
Tudor Oak
Contemporary
Early American
Lt . WalnutSept
Red Mahogany
Br. Mahogany
Gr . Mahogany
Tr. Black
Lt . CherryJan.
Dk. CherryJan.
June
Feb.
Patina Walnut
Med. Cherry
.'59 to Oct . ' 65
Oct. '60 to Oct.
Jan. '61 to Oct.
Jan. '61 to Oct.
Jan . ' 61 to Nov .
'61 to Oct . ' 65
' 61 to Oct . ' 652,
'62 to Oct . ' 65
' 63 to Oct . ' 653,
July' 64 to Oct.
Aug . ' 64 to Oct . '
$2,595.00
' 652, 545.00
' 652, 695.00
' 652,770.00
' 642, 695.00
2.770.00
770.00
2. 995.00
025.00
' 652; 695.00
65 2,770.00
MANUALS :
PEDAL
KEYBOARD :
TONAL 9
CONTROLS :
EXPRESSION:
PERCUSSION:
Swell and Great, 61 playing keys each.
25-note radiating, detachable,
preset keys and 2 sets of 9 adjustable harmonic drawbars
for each manual. 2 adjustable drawbars (16' and 8') for
pedals .
One expression pedal controlling Swell, Great and Pedals.
Four tablets for control of Hammond percussion feature.
REVERBERATION:
One knob control for "off" and all intensities.
DIMENSIONS:
AC INPUT:
OUTPUT :
WEIGHT :
With bench and music rack: 47" wide; 45-1/2" high; 43"
deep .
200 watts.
27 watts E.I.A
Complete 381 lbs.
SC-1
SPECIFICATIONS D-100 SERIES
MODEL STYLE FINISH
IN PRODUCTION
SELLING PRICE
D-152 Tudor Walnut
D-155 Tudor Oak
July '63 to Sept. '69 $3,725.00
July '63 to Sept. '69 3,830.00
MANUALS: Swell and Great, 61 playing keys each.
PEDAL 32-note, concave, radiating, detachable, built to A.G.O.
KEYBOARD: specifications.
PEDAL SOLOHas pedal solo system with separate volume control,
SYSTEM: providing following solo effects; 32-foot Bourdon, 32-foot
Bombarde, 16-foot Solo, 8-foot Solo, 4-foot Solo, 2 and
1-foot Solo. Also tablets for Mute Control and Pedal Solo On
TONAL
CONTROLS :
9 preset keys and 2 sets of 9 adjustable harmonic drawbars
for each manual; for pedals, two adjustable drawbars (16'
and 8 ' ) .
EXPRESSION:
One expression pedal, controlling Swell, Great, and Pedals.
TILT TABLETS: Three providing control of vibrato. Four controlling Hammonc
percussion feature.
REVERBERATION: Two knobs for "off" and all intensities in bass and treble
channels .
DIMENSIONS: Open as shown, 57" wide; 47" high; 48" deep.
AC INPUT: 330 watts.
OUTPUT: 50 watts E.I.A.
WEIGHT: 543 lbs.
SC-2
THE HAMMOND ORGAN
- 2 —
GENERAL DESCRIPTION
&
OPERATING INSTRUCTIONS
|l'i|l | i|
HAMMOND ORGAN COMPANY
North Western Avenue - Chicago
Diversey Ave - Chicago
North 25 th Avenue - Melrose Park
Copenhagen Court - Franklin Park
Illinois
USA
THEORY OF OPERATION
The console of the Hammond Organ contains the entire tone-producing
mechanism, which is completely electrical in operation. Within it are
produced all the tones and tone combinations of the organ. The electrical
waves are made audible, as music, by one or more tone cabinets containing
suitable amplifiers and loud speakers. The block diagrams (Figures 13 and
14) show the chief components of the instrument.
Electrical impulses of various frequencies are produced within a unit known
as the tone generator, containing a number of phonic wheels or tone wheels driven
at predetermined speeds by a motor and gear arrangement. Each phonic wheel is
similar to a gear, with high and low spots, or teeth, on its edge. As the wheel
rotates these teeth pass near a permanent magnet, and the resulting variations in
the magnetic field induce a voltage in a coil wound on the magnet. This small
voltage, when suitably filtered, produces one note of the musical scale, its pitch
or frequency depending on the number of teeth passing the magnet each second.
A note of the organ, played on either manual or the pedal keyboard, generally
consists of a fundamental pitch and a number of harmonics, or multiples
of the fundamental frequency. The fundamental and eight harmonics available
on each playing key are individually controllable by means of drawbars and
preset keys or buttons. By suitable adjustment of these controls the player
is enabled to vary the tone colors at will.
The resulting signal passes through the expression or volume control and
through the preamplifier (where vibrato is introduced) to the tone cabinet.
Here reverberation is added electrically and a power amplifier feeds the
signal into loud speakers.
DESCRIPTION
A Hammond Organ console (Fig. 2) includes two manuals or keyboards: the
lower, or Great, and the upper, or Swell, and a pedal keyboard of 25 keys.
The concert models have a 32-key pedalclavier and are constructed to A. G. 0.
specifications. Various controls have appeared on different models. The operation of
these controls is covered in the following paragraphs.
STARTING THE ORGAN
FIGURE 1
To start the organ, hold the start switch (Fig. 1)
in on position for approximately eight seconds.
Still holding it, push the run switch to on
position. After leaving both switches on for about four
seconds, release the start switch to return to its
normal position.
If the console is very cold, or if a frequency regulator
is used, it may be necessary to hold the start switch
slightly longer.
2
The Concert Model
Hammond Organ
3
PRESET KEYS
At the left end of each manual are twelve keys identical to the playing keys
except reversed in color (Fig. 3). These are replaced by twelve numbered
buttons on the Model E console.
When a preset key is depressed it locks
down and is released only when another
is depressed. The exception to this is
the cancel key at the extreme left, which
serves only to release any key which
may be locked down. Only one preset
key is used at one time. If by mistake
two are depressed and locked, they may
be released by means of the cancel key.
Each preset key, with the exception of
the cancel key and the two adjust keys
at the extreme right of the group, makes
available a different tone color which has been set
up on the preset panel located inside the console. These tone colors are set up at
the factory in accordance with a standard design which has been found to best meet
the average organist’ s requirements. They may be changed, if desired, by removing
the back of the console and changing the preset panel connections in accordance with
instructions on a card located near the preset panel.
When either adjust key is depressed, the organ speaks with whatever tone
color is set up on the harmonic drawbars associated with that key. The
percussion effect on Models B-3, C~3, RT~3, A- 100 & D-100 is introduced when the
upper manual B preset key is depressed (see Percussion also).
HARMONIC DRAWBARS
Each console has four sets of harmonic drawbars, two for each manual. Figure
4 shows one group of harmonic drawbars, by which the organist is enabled
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4
to mix the fundamental and any, or all, of eight different harmonics in various
proportions. The third bar from the left controls the fundamental, and each of
the other bars is associated with a separate harmonic. If a drawbar is set all
the way in, the harmonic it represents is not present in the mixture.
Each drawbar may be set in eight different positions by the organist in
addition to the silent position. Each position, as marked on the drawbars,
represents a different degree of intensity of the harmonic it controls. When
drawn out to position 1, the harmonic it represents will be present with
minimum intensity, when drawn out to position 2, with greater intensity,
and so on up to position 8.
A tone color is logged by noting the numerical position of the various
drawbars. For instance , the tone set up on Figure 4 is known as tone
34 630 5210. After a tone is so logged it may be made available again by setting
the harmonic drawbars to that number.
The drawbars in earlier consoles have distinct intensity positions with
silent spots between them. Later consoles are equipped with continuous
contact drawbar s which move smoothly with no interruption in tone.
HARMONIC DRAWBARS FOR THE PEDALS
In the pedals the harmonic resources have been combined into two drawbars
which may be used separately or in combinations. When the left drawbar is
used emphasis is given to the lower harmonics, and similarly the higher
harmonics are emphasized when the right drawbar is used. The pedal drawbars
are located between the two sets of manual drawbars.
PEDAL TOE PISTONS - CONCERT MODEL E CONSOLE
FIGURE 5
Four pedal toe pistons are located to
the left of the expression pedals. Numbers
one and two of these pistons are
pedal presets. The third is a Great-to-Pedal
coupler, which makes the pedals
speak with whatever 8 foot tone is set
up on the Great manual. The left pedal
drawbar may be used with the coupler
to add 16 foot tone. The fourth piston
connects the pedals to the two pedal
drawbars.
Lighted piston indicators are provided on the left side of the console just above
the Swell manual. Each time a toe piston is depressed, the proper indicator is
automatically illuminated so the organist always knows which toe piston is
depressed.
5
PEDAL SOLO UNIT - MODELS RT, RT-2, RT~3, and D-100
A pedal solo unit is incorporated in the Concert Models with prefix RT and D to
provides a series of bright pedal solo tones in addition to the usual pedal
accompaniment tones available on other models. The pedal solo tones, generated by a
vacuum tube oscillator circuit, are controlled by a volume control knob and eight
tilting stop tablets located at the right end of the Great manual (Fig. 5). One
tablet turns all the pedal solo tones on or off and the others provide various pitch
registers and tone colors. The pedal solo unit is independent of the electromagnetic
tone generator and can be turned off without affecting the remainder of the organ.
NORMAL - SOFT VOLUME CONTROL
(Models B-2, B-3, C-2 (G) , C-3, RT-2, RT-3, A-100, D-100)
This control (upper left, Fig. 3) is a tilting tablet which supplements the action
of the expression pedal. In soft position it reduces the volume of the whole
instrument. It is particularly useful when playing in a small room or when
the organist wishes to practice without disturbing others.
CHORUS CONTROL
(Models BC, BCV, D, DV, E, G)
On these models an extra generator known as a chorus generator will be
found. To use the tones generated by this unit at will, one extra black
drawbar has been added which operates a switch located on the generator.
The drawbar labeled chorus is located at the right-hand end of the console.
(Fig. 6)
When the organ is played with the chorus drawbar pushed in (the off position)
it operates in exactly the same way as though no chorus were included. Pulling
the drawbar out (to the on position) instantaneously adds the ensemble or
chorus effect to whatever is being played. Actually it adds a series of slightly
sharp and slightly flat tones to the true tones produced by the main generator.
The resulting electrical wave contains a complex series of undulations which
enhance the pleasing effect of many tone qualities, notably string and full
organ combinations.
The chorus control should not be confused with the vibrato chorus effect,
described under vibrato. . The two effects are similar musically, but are
produced by completely different means.
EXPRESSION OR SWELL PEDAL
The swell pedal, located in the customary position, is operated by the right
foot and with it the volume of the organ may be controlled over a wide range.
It operates on the two manuals and pedals equally; that is to say, once the
manuals and pedals are balanced, they retain their relative balance over
the entire swell pedal range.
6
Two expression pedals are provided for the Model E Console. Both are
equipped with adjustable clamps to regulate the tension and the distance
through which they move. Adjustable pedal indicators, operated by wires
from the rheostat box, are located at the extreme right side of the console
above the Swell manual.
ECHO SWITCH
Located above the starting and running switches
on some consoles is the echo switch (Fig. 6).
With this switch it is possible to use two tone
cabinets and have either cabinet or both speak,
depending on the position of the switch. Generally
one tone cabinet is placed rather distant from
the console and is called the echo organ. This
feature can be added to a Hammond Organ by
installation of an Echo switch kit.
FIGURE 6
TREMULANT
The tremulant or tremolo is a periodic variation in intensity of all tones
without change in pitch. It is produced by a variable resistance driven by
the motor of the main tone generator, and is controlled by a variable resistor
in shunt. When the tremulant control is turned as far as possible to the left,
the tremulant is entirely off. As it is turned to the right (clockwise) the degree
of tremolo gradually increases until it reaches a maximum at the extreme right
position. The white dot marker on the knob indicates at a glance the degree of
tremolo present. Two tremulant controls are used on the Model E console, one
for each manual. These are controlled by separate levers located on the console.
The tremulant is not incorporated in models having vibrato.
VIBRATO
The vibrato effect is created by a periodic
raising and lowering of pitch, and thus is fundamentally
different from a tremolo, or loudness
variation. It is comparable to the effect
produced when a violinist moves his finger
back and forth on a string while playing,
varying the frequency while maintaining
constant volume.
The vibrato mechanism includes an electrical time delay line,
which shifts the phase of all tones fed into it. A rotating
scanner, mounted on the main tone generator, picks up successive signals from
various line sections. These signals represent various amounts of phase shift, and
the combination of signals produces a continuous frequency variation.
FIGURE 7
7
When the vibrato chorus switch (Fig. 7) (Models AV, BV, BCV, CV, DV, and RT) is
pushed to the left, normal vibrato is obtained with the vibrato switch in positions
1, 2, or 3. When the lever is pushed to the right a chorus or ensemble effect,
combining foundation organ tone with vibrato tone, is obtained. The center position
of this switch is not intended to be used. No harm will result from leaving the
switch in this position, but reduced volume will be obtained.
Models B~2, B-3, C~2 (G) , C~3, RT-2, RT-3, A-100 & D-100 have the selective vibrato
feature which makes the vibrato effect available on either manual separately
or on both together. Two tilting tablets (Figure 3) control the vibrato for the
two manuals, while the rotary switch selects the degrees of vibrato or vibrato
chorus effect. The Great tablet controls the vibrato for the pedals as well as
for the Great manual.
The vibrato is not present on models having the tremulant.
PERCUSSION
The Percussion feature (Models
B~3, C~3, RT~3, A-100, and D-100) is controlled
by four tilting tablets (Fig. 8) at the upper right
side of the manuals. Percussion is available only
on the upper manual and only when the B
preset key is depressed. The four tablets (from
left to right) select Percussion on or off, normal
or soft Volume, fast or slow Decay, and second or
third Harmonic tone quality.
Percussion tones are produced by borrowing the
second or third harmonic signal from the corresponding manual drawbar, amplifying
it, returning part of the signal to the same drawbar, and conducting the balance of
the signal through push-pull control tubes where its decay characteristics are
controlled.
The Percussion signal is then combined with the signal from the manuals after the
vibrato but before the expression control. The control tubes are keyed through the
eighth harmonic key contacts and busbar.
FIGURE 8
TONE GENERATOR
The main tone generator furnishes 82 or 91 different musical frequencies,
depending on the console model. It includes a tone wheel, magnet, and coil
for each frequency. Mounted on top of the generator are tuned filters to
insure purity of the tones.
PREAMPLIFIER
The preamplifier is located in the console. Several types have been used
in the various console models. Some obtain their plate voltage from the
power amplifier through the console-to-cabinet cable, while others have a
self-contained power supply.
TONE CABINETS
Tone cabinets are made in a number of models differing in size, finish, and
power output. The numbers 20 and 40 in the model designations indicate the
nominal power output in watts. Each tone cabinet includes one or two power
amplifiers and two or more speakers.
Cables of special design are used to connect the console to the tone cabinet
or cabinets.
REVERBERATION CONTROL
Tone cabinets having the letter R within the model designation are equipped
with the Hammond Reverberation Control. This is an electro-mechanical
device designed to supply reverberation for installations that are acoustically
dead or have insufficient natural reverberation. A portion of the
musical signal is delayed by passing through fluid-damped coil springs and
then combined with the direct signal. By adjustment of the amount of
delayed signal the reverberation characteristics of large or small enclosures
may be simulated. A tone cabinet having this unit must be handled in accordance
with directions on the instruction card in order to avoid damaging the
unit or spilling the fluid.
ROTOR TREMULANT
Tone cabinets having the letter X in their model designation contain a drum
rotor mounted above the speakers and driven by a small motor. Rotating in
the path of sound from the loud speakers, it produces the effect of a periodic
volume and pitch variation in all tones of the organ.
A switch for controlling its operation can be mounted on the tone cabinet, or
an additional cable with a switch located at the console may be used.
When a console having the Hammond Vibrato is connected to this type cabinet,
use of the rotor tremulant is not recommended.
9
INSTALLATION AND MAINTENANCE
The organ must be connected to a regulated frequency source of the
voltage and frequency specified on the name plate. If the frequency is
not regulated the pitch of the organ will be irregular.
When a console is set up for operation the anchoring must be loosened so that
the generator will float freely on its spring suspension system. No damage
will result if this is not done, but the console will sound noisy, and the same
is true if the anchoring is loosened but the console is not level. If the console
is to be moved a long distance the anchoring should be tightened during such
moves.
Several different types of anchoring have been employed and instructions for
loosening and tightening the generator in any particular console are given on
the instruction card contained in the bench which accompanied that console.
Each power amplifier has anchoring which should be loosened on installation
and tightened for shipping. If the cabinet has a reverberation unit, it should be
locked before moving the cabinet and the fluid should be removed as instructed
on the card attached to the tone cabinet.
The tone generator is lubricated by putting oil into cups inside the console. It
is recommended that each cup be filled three-fourths full, (1 tablespoon) once
a year, using only the oil recommended for this purpose.
POWER AMPLIFIER
A-100
A twelve watt amplifier is mounted on the lower shelf of the console. It receives
the signal from the Preamplifier and increases it in power to drive the two 12 "
speakers.
D-100
A fifty watt three channel amplifier (bass with reverberation, treble, treble
with reverberation) together with its independent power supply is located on
the lower shelf of the console. It receives the signal from the preamplifier
and furnishes power to drive the 2 - 12 " speakers and 2 ~ 8 " speakers.
C2-G
These consoles are identical in appearance to the C-2 and C~3 except that a monitor
speaker is located on the lower left hand side. The preamplifier in the C-2G is
designed to operate the monitor speaker. In the C~3G the preamplifier is the same as
in the C~3. A small auxiliary amplifier drives the monitor speaker. In both Models,
B+ voltage from the tone cabinet is required to make the monitor speaker operative.
The HR-40G is identical to the HR-40 except that it is equipped with a standard 6
conductor cable which must be used in conjunction with the C-2G console.
10
REVERBERATION SYSTEM
A-lOO
To the left of the amplifier are the reverberation amplifier and reverberation unit.
A portion of the output signal of the power amplifier passes through the
reverberation unit to the reverberation amplifier and this drives a third ^"'speaker
housed within the console. The degree of reverberation heard can be regulated by
rotating the knob marked Reverberation Control located above the Vibrato tabs on
the left side of the console.
D-100
To the left of the pedal solo generator is the Hammond Reverberation unit. Signals
from the preamplifier are applied to the treble with reverberation channel
of the power amplifier and are heard from the 8” speaker located to the right
of the player.
In operation, an electrical signal from the reverberation drive channel is applied
to the driver unit in the reverberation device which then converts the
electrical signal into mechanical energy. This energy is transmitted through
springs to a pickup unit where a part of it is converted back to electrical
energy. The remaining portion is reflected back to the driver and again back
to the pickup at a time interval determined by the spring lengths. This transaction
continues until the signal energy is reduced to one millionth of its original value.
The transfer time from driver to pickup and the reflections within the system itself
produce the reverberation effect. The degree of reverberation heard can be regulated
by rotating the knob marked Reverberation Control shown in Figure 5.
11
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FIGURE 1 2 REAR VIEW OF RT-3 (WITH PERCUSSION).
16
Typical Rear View of a Model A-1 00
ADJUST KEYS H DRAWBARS
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FIGURE 7 BLOCK DIAGRAM OF ORGAN MODEL A- 1 00
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21
THE HAMMOND ORGAN
-3-
ACOUSTICS
HAMMOND ORGAN COMPANY
North Western Avenue - Chicago
Diversey Ave - Chicago
North 25 th Avenue - Melrose Park
Copenhagen Court - Franklin Park
Illinois
USA
ACOUSTICS
THE PART THEY PLAY IN HAMMOND ORGAN INSTALLATIONS
INSTALLATIONS IN GENERAL:
The proper installation of a Hammond organ requires the careful observance of
four primary rules:
1. The organ should furnish AMPLE POWER.
2. The sound energy from the organ should be EVENLY DISTRIBUTED.
3. The console and tone cabinets should be so located in relation to each other and
to the audience, choir, soloist, etc. , that a PROPER TONAL BALANCE is
accomplished.
4. The organ tone should be PROPERLY REVERBERATED.
The observance of these rules with due consideration to the particular use for which
the instrument is required will insure the best possible installation in any type of
enclosure. These rules will be discussed in detail in the following pages.
POWER
There are so many factors which have a bearing on the amount of power or sound
energy necessary for best musical results in a given enclosure that an accurate
formula for determining the required power in all cases would be too cumbersome for
everyday use. Experience has shown that it is very seldom that too many tone
cabinets are specified. Therefore, if there is doubt as to the sufficiency of tone
cabinets for any installation it is reasonably safe to double this amount. This will
greatly improve the musical quality of the instrument and eliminate overloading of
the speakers. Some of the factors which have a bearing on the amount of tone cabinet
equipment required in any enclosure are the size and shape of the enclosure,
placement of tone cabinets, amount and location of sound-absorbing materials
including persons present in the enclosure. The use for which the organ is desired
also has a bearing on requirements; for example, an organ to be used primarily to
support congregational singing would require more tone cabinets than one that is to
be used mainly for accompaniment of soloists or light entertainment.
The following conditions in an enclosure, therefore, usually indicate that more than
an average installation may be required:
1. When the area of the boundaries of the enclosure is great in proportion to the
volume of the enclosure. Thus, an enclosure of irregular shape having numerous
alcoves, etc. .would require more tone cabinets than one of cubical shape.
2. When the tone cabinets are located in a position where considerable sound
absorption takes place before the music reaches the listener. A poorly designed or
constructed organ chamber is an example.
3. When acoustical correction materials are used on walls or ceiling, when heavy
drapes are present and carpets are used for floor covering.
4. When seating capacity is high for the size of the enclosure. For practical
purposes an open window is considered as an area of 100 percent absorption of sound.
A single person absorbs about as much sound as four square feet of open window.
Therefore, an audience of 1,000 people will have the effect on music volume of an
open window area of 4, 000 square feet as compared with the volume heard when the
enclosure is empty. To offset this absorption, a disproportionately greater amount
of tone cabinet equipment must be used.
1
DISTRIBUTION
The sound energy from the organ should be distributed as evenly as possible
throughout the enclosure. In order that this may be accomplished, it is important
that the sound be distributed in the auditorium above the listeners and that a large
percentage of the sound reaching the listener is by numerous reflections from the
walls and ceiling. Direct projection as well as direct reflection from the speakers
should not reach the listener. Focusing effects of curved surfaces such as barreled
ceilings often cause difficulty in sound distribution unless the tone cabinet is so
located as to reduce the direct sound energy that reaches these surfaces.
It must be remembered that although sound is reflected in a manner similar to light,
the reflecting surface must be large in relation to the wave length of the sound.
Therefore, a reflecting surface of a given size will reflect sounds above a certain
frequency, while sounds of lower frequency will be diffracted or spread out. To
reflect fully the lower tones of the organ a reflector thousands of square feet in
area is necessary. This, together with the fact that different materials absorb
sounds of certain frequencies more than others explains why identical tone colors
produced in different enclosures will sound very different to the ear.
BALANCE
The placement of console and tone cabinets should be carefully planned so that the
following conditions are fulfilled:
1. The organ should sound as loud or slightly louder to the organist at the console
than it does to the audience. This allows the organist to accurately judge the
musical effect he is producing and make any necessary corrections before the
audience appreciates the need for them. It also reduces the tendency of playing too
loud which is usually evident when the organist hears the organ at a lower level
than the audience.
2. The organist should hear the organ and the choir with the same relative loudness
that the audience hears them, otherwise a perfect tonal balance between organ and
choir from the organist’ s point of hearing will result in an unbalanced effect as
heard by the audience. When we refer to the choir we also include instrumental
groups or soloists who may have occasion to perform in conjunction with the organ.
3. The tonal equipment of the organ should be so located that the choir, while
singing, has adequate support from the organ when played at accompaniment volume.
They should not, however, hear the organ so loudly as to have difficulty in singing
with it. Good tonal balance and ease of performance should result if the average
distance between choir and tone cabinets is about the same distance as between tone
cabinets and organist.
4. The audience should hear the choir and the organ as a balanced ensemble, and
the tone cabinets should be so placed that the choir voices will not be obscured by
the organ tones.
REVERBERATION
Reverberation is the prolongation or persistence of sound by reflection, what we
usually mean by echo. It is measurable by the interval of time required for the
sound to decay to inaudibility after the source of the sound has been stopped. It is
present in a varying degree in all enclosures and most types of music are more
pleasing to the ear when accompanied by a certain amount of reverberation.
2
It is also the most important single factor to be considered in planning an organ
installation as proper reverberation makes it easier to attain all of the other
requirements necessary for a perfect installation.
In a Hammond organ installation, the proper amount of reverberation may be secured
in three ways:
1. By the successive reflections of the sound by the boundaries of the auditorium.
2. By the Hammond Reverberation Control.
3. By placing the tone cabinets in a chamber, the boundaries of which cause the
organ tones to reverberate before reaching the auditorium.
REVERBERATION IN THE AUDIITORIUM
The reverberation that results from the successive reflections of sound back and
forth by the boundaries of the auditorium itself is most desirable from the
installation engineer’ s point of view. (By auditorium we mean any audience room such
as a church or concert hall. )
In a reverberant auditorium less power is necessary and problems of sound
distribution are greatly simplified and, therefore, the best possible musical
results are usually obtained as a matter of course. Unfortunately, however, the
reverberation characteristics of an auditorium usually are not alterable by the
installation engineer, and he must accept them, good or bad as the case may be.
A reverberation time of one second when a two-thirds capacity audience is present is
usually sufficient if reasonable care is taken in locating the organ equipment for
proper distribution and balance although a slightly longer reverberation time is
often desirable. It must be remembered that the reverberation time in any enclosure
is greatly reduced when an audience is present. In general, the higher the ceiling
of the auditorium, the less effect the presence of an audience has on the
reverberation time; however, this effect is always considerable. If the natural
reverberation in the auditorium is insufficient for best musical results from the
organ, another method must be used to properly reverberate the organ tones.
HAMMOND REVERBERATION CONTROL
The Hammond Reverberation Unit provides an effective means of securing proper
reverberation in all types of installations where the natural reverberation in the
auditorium is insufficient. Experience has shown that best installations in homes,
radio studios, mortuaries, and small churches include a tone cabinet equipped with
reverberation control. It may also be used to improve the effectiveness of the organ
in auditoriums where considerable natural reverberation is present, but where this
natural reverberation is characterized by an objectionable echo occurring after the
organ tones have seemingly ceased. The Hammond Reverberation Unit will not eliminate
an echo or reduce the natural reverberation time, but will often make this natural
reverberation more pleasing to the ear by filling in that period between the time
the organ tones seem to cease and the echo occurs. The Hammond Reverberation Unit
will not add to the reverberation time in auditoriums already having excessive
natural reverberation. As the reverberation unit is connected to the electrical
system of the organ and provides reverberation at the source of sound rather than
after the sound comes from the speakers, it allows the installation engineer to
place the tone cabinets for best results in balance and distribution without the
necessity of compromise for reverberation considerations.
3
The use of this device also eliminates the necessity of costly reverberation
chambers, and by allowing the tone cabinets to be so located as to minimize sound
energy losses, a saving in the amount of necessary power equipment is often
effected. A further advantage is that the reverberation time may be regulated for
best musical results after the organ is installed. With the use of the Hammond
Reverberation Unit a good organ installation should always result if the tonal
equipment is placed to give even distribution and proper tonal balance.
REVERBERATION CHAMBERS
When it is desired to conceal the organ tone cabinets and there is adequate space
available, a properly designed reverberation chamber may be very effective in
supplying reverberation for the organ tones. In many cases, however, the space
allotted for use as a reverberation chamber is anything but ideal, and often,
because of structural limitations, little can be done to improve the effectiveness
of the chamber other than to make minor corrections. The following principles of
reverberation chamber design are given for guidance in properly evaluating the good
and bad characteristics of a given chamber and in making such changes as will
improve the effectiveness of the chamber as much as possible.
SIZE
As the reverberation time increases as the size of the chamber increases, the
chamber should be as large as possible. Experience has shown that practically the
only exceptions to this rule are when the shape of the chamber may be improved by
reducing its size or when the tone opening cannot be made large enough in proportion
to the size of the chamber. For best musical results the chamber should be at least
800 cubic feet in volume. The dimensions of the chamber are in most cases ideal if
they are in the ratio of approximately 2 : 3 : 4 x h. A chamber of equal volume but
more cubical in form would have a longer reverberation time, while a chamber of less
cubical form would have a shorter reverberation time; however, dimensions in the
above ratio usually are most desirable. Chambers of complex shape or chambers of
regular shape whose greatest dimension is more than three times the least dimension
should be avoided.
4
CHART SHOWING SIZE OF TONE OPENING REQUIRED
FOR REVERBERATION TIME OF ONE SECOND
FOR CHAMBERS WITH DIMENSIONS IN RATIO OF 2 : 3 : 4.5
VOLUME OF CHAMBER IN CUBIC FEET
FIGURE I.
CONSTRUCTION AND FINISH
All boundaries of a reverberation chamber should be of exceptionally rigid
construction. Concrete or heavy tile is ideal. If the chamber is to be of frame
construction the studs should not be over fourteen inches on centers. Lath should be
very securely nailed and the plaster should be hard and given a smooth finish coat.
TONE OPENINGS
The reverberation time of an organ chamber is greatly influenced by the size of the
tone opening. For a chamber of given dimensions, the reverberation time is increased
as the area of the tone opening is reduced. A large chamber, therefore, may have a
large tone opening and still furnish sufficient reverberation, whereas a small
chamber might require a very small opening. A chart is shown in Figure 1, giving the
area of tone opening required to furnish one second reverberation time when the
volume of the chamber is known. This chart is for chambers with dimensions in the
ratio of 2 : 3 : 4 14 only; however, in practice the areas of tone opening shown are
generally satisfactory. The tone opening should be located in the largest wall
surface of the chamber if possible, and preferably near the center of the wall area.
5
THE HAMMOND ORGAN
-4-
CABLES & PLUG ASSEMBLIES
&
CABLE CONNECTION DIAGRAMS
|l'i|l | i|
HAMMOND ORGAN COMPANY
North Western Avenue - Chicago
Diversey Ave - Chicago
North 25 th Avenue - Melrose Park
Copenhagen Court - Franklin Park
Illinois
USA
CABLES
Each console is shipped from the factory with cables sufficient for an
ordinary installation having a single tone cabinet. It has a 15 foot 2 conductor
line cord for connecting to an AC wall outlet, and a 35 foot console-to-cabinet
cable (6 conductor or 5 conductor, depending on the console model) to connect
to the first power amplifier. In case the console is located an unusually long
distance from the tone cabinet, additional 6 or 5 conductor cable must be
ordered. If the console has an echo switch, a 5 conductor cable of the required
length must be ordered separately to connect it to the echo tone cabinet. (See
Echo Organ Wiring, on page 3 of this section).
For installations having two or more tone cabinets, cable suitable in length
must be secured to connect between cabinets. Each power amplifier has a 6
pole input plug and a 5 pole coupling receptacle for connecting additional
amplifiers.
TYPES OF CABLES USED
6 Conductor console-to-cabinet cable used onion models A, B, AB, BC,
BCV, BV, C, CV, D, DV, E, G, RT. This is used only between these models
of consoles and the first power amplifier, and has a 6 pole plug at one end and
a 6 pole receptacle at the other. It consists of two AC wires, two grid (signal)
wires, a B plus wire to carry plate current from the first power amplifier to
the console preamplifier, and a ground (signal return) conductor, which is
actually a shield over the B plus wire. This cable is especially designed for
use with the Hammond Organ and is approved by the Underwriters Laboratories
for that purpose.
5 Conductor console-to-cabinet or cabinet-to-cabinet cable. This is identical
to the 6 conductor cable except that it has no shield and one end has a 5 pole plug
instead of a 6 pole plug. It has no B + conductor, the fifth wire being used for
ground. It is used for carrying power and signal between amplifiers, since a B +
connection is never needed beyond the first power amplifier; to connect an
echo cabinet, since in this case also no B + connection is required; and as a
console-to-cabinet cable for models where the console preamplifier has its own
power supply. In case 5 conductor bulk cable is not available, a 5 conductor cable
assembly may be made from 6 conductor bulk cable, using the shielded wire for
ground and leaving the shield disconnected. NOTE: 5 conductor console -to-cabinet
cable is used with Models B-2, B-3, C~2, C~3, RT-2, RT-3, A- 100, and D-100.
3 Conductor cabinet -to -cabinet cable. This is used for carrying only the
signal between amplifiers, and is used for connecting cabinets when external AC
power circuits are employed. It is standard 3 conductor indoor telephone cord
and has 5 pole plugs on both ends. A cable may be made up with a number of
plugs along its length in order to connect several cabinets together. This wire
can be secured from your local electrical jobber.
1
2 Conductor line cord. This supplies AC power to the console and has a
standard attachment plug on one end and a standard attachment receptacle on
the other.
2 Conductor cabinet power cord. This is used to furnish AC power to additional
power amplifiers, when the signal is supplied through a 3 conductor signal cable.
It has a standard attachment plug at one end and a 6 pole receptacle at the other.
For permanent installations, when the cables are to be installed in conduit,
special Jones fittings manufactured by the Cinch Manufacturing Company are
obtainable through your electrical supplier. Those recommended for console
location are:
1-5406 - CCE 6 prong socket
1-P406-WP 6 prong plug with wall plate
For each tone cabinet location:
1-P406 - CCE 6 prong plug
1-5406 -WP 6 prong socket with wall plate
BLOCK DIAGRAMS
Figure 1 is a simplified diagram showing how the console is connected to
a single tone cabinet or group of cabinets drawing not over 620 watts input.
This is the maximum AC power which can be supplied through the console
without damaging the console switch or wiring. The name plate on each cabinet
shows its wattage rating.
If the tone cabinet power requirements exceed 620 watts, some of the cabinets
must be supplied from a separate AC source as indicated in figures 2 and 3.
Figure 2 is the preferred method, employing a relay to turn on the additional
cabinets. The relay must have a coil of the same voltage and frequency rating
as the organ, and must have contacts suitable for carrying the amount of power
drawn by the additional cabinets. AllenHBradley Bulletin 700 relays are suitable
for this purpose and may be obtained from your electrical supplier.
When the AC power is supplied separately to additional cabinets, as in figures
2 and 3, a 3 conductor cable is sufficient to carry the signal between cabinets.
DETAILED WIRING DIAGRAMS
Figures 4, 5, and 6 are detailed versions of figure 1. In figure 4 the console is
connected to one tone cabinet having a single amplifier, and figure 5 shows
connections to a cabinet with two power amplifiers, connected together by a 5
conductor coupling cable. Additional amplifiers up to a maximum of 620 watts AC
input, may be connected as shown in Figure 6.
2
Figure 7 is a detailed diagram of the arrangement in figure 2. The 3 conductor
cable carries signal to all cabinets, while each cabinet has its own AC power cord.
In this case the 6 pole input plug in each additional cabinet is used for power
input only, and the signal is fed, into the 5 pole coupling receptacle.
A switch may be connected in place of the relay contacts to convert this circuit
to the arrangement of Figure 3.
ECHO ORGAN WIRING
Some desirable musical effects may be secured by an echo tone cabinet installed
at a location some distance from the main cabinet or cabinets. As indicated in the
block diagram, Figure 8, an echo switch on the console controls only the tone
cabinet signal circuits, and all cabinets remain energized so that they will sound
instantly when desired. Figure 9 shows the cable connections required.
REVERBERATION EQUIPMENT
Some types of tone cabinets have reverberation units and reverberation preamplifiers
built into them. In this case, see the instruction card attached to the cabinet for
correct cable connections. While there are several different styles of wiring, it
will be found that every cabinet has a 6 pole input plug and a 5 pole output
receptacle for connecting additional amplifiers. Some reverberation preamplifiers
employ a special detachable coupling cable, wired as shown at the bottom of
Figure 10.
In reverberation-equipped tone cabinets type CR-20, DR-20, ER-20, FR-40,
and G -40, reverberation is applied to all organ frequencies. In this case only
one reverberation unit is required for any installation, no matter how many tone
cabinets are used. The reverberation unit should be in the cabinet which is
connected directly to the console, in order that reverberated signal may be supplied
by it to all other cabinets.
In multi-channel tone cabinets type JR-20, HR-40, KR-40, PR-20, PR-40
and QR-40 a reverberated signal is not available to drive succeeding cabinets. For
this reason an installation using several such cabinets must have a reverberation
unit in each cabinet if it is desired that reverberation be present in all
cabinets.
It is not recommended that multi-channel cabinets be driven by a reverberated
signal from a preceding cabinet because irregularities in the bass response
of the reverberation system may be emphasized by the bass amplifier channel.
In case one of these cabinets is to be used with one or more reverberation cabinets
of other types, it should be connected directly to the console, with the other
cabinets following it in the usual way.
Further information on types of reverberation equipment will be found in
the section dealing with this item.
3
4
-2-POLE PLUG
, IN CONSOLE /
-5 OR 6-POLE RECEPTACLE
IN CONSOLE
6-POLE PLUG FOR
CONSOLE CABLE -
POWER AMPLIFIER
A.C.LINE CORD
(2-POLE ATTACHMENT
PLUG ON ONE END;2-
POLE RECEPTACLE ON
OTHER)
-5-POLE RECEPTACLE
FOR ADDITIONAL
AMPLIFIERS
-5 OR 6-CONDUCTOR CONSOLE-
TO-CABINET CABLE (S-OR6-
POLE PLUG ON ONE END;
6-POLE RECEPTACLE ON OTHER)
TONE CABINET TYPE A20.C2O,
CR20.D20.DR20, ER20 (OR
LATER TYPE H40 OR HR40
WITH SINGLE AMPLIFIER)
FIGURE 4. DETAILS OF CONNECTION OF CONSOLE TO TONE
CABINET WITH ONE AMPLIFIER
(FOR CONNECTIONS OF CABLES TO PLUGS AND RECEPTACLES, SEE FIGURE 10)
5-CONDUCTOR COUPLING
CABLE (5-POLE PLUG ON
ONE END; 6-POLE
RECEPTACLE ON OTHER) -
TONE CABINET TYPE
A40, B40,G40, F40,
FR40.640 (OR EARLY
TYPE H40 OR HR40
WITH 2 AMPLIFIERS)
-POWER AMPLIFIERS
5 OR 6-CONDUCTOR
CABLE FROM CONSOLE
FIGURE 5. DETAILS OF CONNECTION TO TONE CABINET
WITH TWO AMPLIFIERS
(for CONNECTIONS OF CABLES TO PLUGS AND RECEPTACLES, SEE FI6URE 10)
5
2,3,OR 4 POWER AMPLIFIERS
. (IN 2,3,OR 4 CABINETS, DEPENDING ON TYPE)
(total A.C. POWER TAKEN BY All CABINETS drawing power
THRU CONSOLE WIRING MUST NOT EXCEED 620 WATTS)
/ \
5 OR 6-CONDUCTOR CABLE
FROM CONSOLE
5-COND
CABLE
5-COND.
CABLE
S-COND.
CABLE
6-POLE
PLUG
5-POLE
RECEPTACLE
FIGURE 6. DETAILS OF CONNECTION TO TWO OR MORE
TONE CABINETS WITH TOTAL OF NOT OVER 620 WATTS A.C. INPUT
(FOR CONNECTIONS OF CABLES TO PLUGS AND RECEPTACLES, SEE FIG. 10)
FIRST CABINET OR CABINETS, TOTALING
NOT OVER 620 WATTS A.C. INPUT,
CONNECTED DIRECTLY TO CONSOLE
AC. POWER
SOURCE
5-COND.
CABLE
5 OR 6-CONDUCTOR
CABLE FROM CONSOLE
2 CONDUCTORS
(AG. POWER TO RELAY COIL)
ALL COROS CONNECTED-
IN PARALLEL TO OUTLET
3-CONDUCTOR CABLE
(SIGNAL ONLY)
(5-POLE PLUGS ON
BOTH ENDS)
-2-COND. POWER CORDS
(6-POLE RECEPTACLE ONE END;
2-POLE ATTACHMENT PLUG
ON OTHER)
3-COND.
(SIGNAL ONLY)
— 5-COND.
3-COND.
(SIGNAL ONLY)
6-POLE PLUG
ANY NUMBER OF ADDITIONAL TONE CABINETS
FIGURE 7. DETAILS OF TYPICAL INSTALLATION
OF TONE CABINETS WITH A.C. INPUT
TOTALING MORE THAN 620 WATTS
(FOR CONNECTIONS OF CABLES TO PLUGS AND RECEPTACLES, SEE FIGURE 10)
5-POLE
RECEPTACLE
6
INDICATOR
INDICATOR
1
SIGNAL
SIGNAL
n
1
BROWN
BROWN
1
GREY
A C. POWER
GREY
A.C. POWER A.C. POWER
6 POLE RECEPTACLE
CTOR C0N50LE-T0-CABINET ;
GREY
A.C. POWER
I 5
32 4 c
BLUE
A.C. POWER
| YELLOW OR BROWN
GROUND
5 POLE PLUG
NO connection
BLUE
A.C.POV?*iR
YELLOW OR BROWN
GROUND
GREY
A C. POWER
5 POLE PLUG 6 POLE RECEPTACLE
5 CONDUCTOR CABINET -TO- CABINET, CONSOLE-TO-CA BlNET, OR AMPLlFtER-TO- AMPLIFIER COUPLING CABLE
INDICATOR INDICATOR
GREEN-YELLOW TR.
SIGNAL
NO CONNECTION
GREEN-RED TR.
GREEN-YELLOW TR.
GREEN-RED TR,
SIGNAL
NO CONNECTION
1 GREEN GREEN |
GROUND GROUND
5 POLE PLUG 5 POLE PLUG
3 CONDUCTOR CABINET -TO- CABINET OR AMPLIFIER-TO-AMPLIFIER SIGNAL CABLE
INDICATOR
NO CONNECTION
NO CONNECTION
6 I
35 2C
4 3 .
NO CONNECTION
| NO CONNECTION
GREY
STANDARD ATTACHMENT PLUG
FOR CONNECTION TO A.C. OUTLET
> POLE RECEPTACLE
2 CONDUCTOR AMPLIFIER POWER CORD
BLACK (SHIELDED)
SIGNAL
RED (5HELDED)
SIGNAL
BLUE
A.C. POWER
RED (SHIELDED
SIGNAL
BLUE
A.C. POWER
BLACK (SHIELDED)
SIGNAL
YELLOW
SHIELD (6ND)
GREY
A.C. POWER
NO CONNECTION
7 POLE PLUG 6 POLE RECEPTACLE
> CONDUCTOR REVERBERATION- PREAmPUFIER-TQ-POWER -AMPLIFIER COUPLING CABLE
CABLE CONNECTOR WIRING
FIGURE 10
ALL VIEWS SHOW BACK OR CABLE SIDE OF CONNECTOR
7
EXTENDING SPEAKERS.
When using one or more 20-watt kits in an installation it is sometimes
necessary, because of lack of space or for convenience in future servicing,
to place the amplifiers some distance from the speakers. Should this become
necessary, the leads to the speakers can be consolidated in four conductors.
Figure 11 shows how this is accomplished, using the two male plugs on the
speakers. In this arrangement the stud connections are not necessary.
The conductors used for this extension must have insulation to withstand
300 volts and wire size should not be less than # 14. Ordinary # 14 house wiring
wire, with rubber or plastic insulation, is suitable.
(VIEWS OF CABLE SIDE OF PLUGS)
6 POLE PLUG
5 POLE PLUG
FIGURE 1 1
THE HAMMOND ORGAN
-5-
MAIN GENERATOR
HAMMOND ORGAN COMPANY
North Western Avenue - Chicago
Diversey Ave - Chicago
North 25 th Avenue - Melrose Park
Copenhagen Court - Franklin Park
Illinois
USA
TECHNICAL SECTION
MAIN GENERATOR - GENERAL DESCRIPTION
Each Hammond Organ console has a main generator within it, and in
some cases, depending on the model, a chorus generator. This section
describes a main generator, illustrated (generically) below.
■iCT.inMllIIlIto
V OIL
OIL HERE
FUNNEL
OIL »
HERE OIL
FUNNEL
OIL
HERE
CHORUS OIL TUB
VIBRATO OVER
SCANNER RUN MOTOR
RUN MOTOR
M3 Tone Wheel Generator
www.ORGANSTUFF.com
START MOTOR
and CLUTCH
ASSEMBLY
The main generator assembly consists of the generator proper, a shaded
pole induction motor for starting, a non self-starting synchronous motor
for driving the unit after it is started, and either a tremulant switch
mechanism or a Vibrato Scanner mounted on the synchronous motor. The
entire assembly is mounted on two long steel angles which also provide
the means of mounting the tone generator in the console. The method of
mounting is such as to minimize the transmission of vibration from the
tone generator to the console.
A drive shaft, resiliently coupled to the synchronous running motor, extends
the entire length of the generator. Twenty-four driving gears, two each of
twelve sizes, are mounted on this shaft, and the drive shaft itself is divided
into several sections connected by flexible couplings. The starting motor
is mounted at the end of this drive shaft, opposite the synchronous motor.
Section 7 (Console Power Wiring) describes the starting procedure.
The main generator proper is a long structure in which are mounted 48
rotating assemblies, each consisting of a shaft and two discs known as
tone or phonic wheels. These assemblies are coupled resiliently to the
drive shaft. Each of the driving gears engages two bakelite gears
associated with opposite rotating assemblies (See Figure 2). These
bakelite gears rotate freely on the shafts with the tone wheels, and are
coupled to their respective assemblies by a pair of coil springs. There
are 12 sizes of bakelite gears, corresponding to the 12 sizes of driving
gears. Thus 4 of the tone wheel assemblies, each with 2 tone wheels, run
at each of 12 speeds.
1
Each tone wheel is a steel disc about 2 inches in diameter, accurately
machined with a definite number of high and low points on its edge
(See Figure 3). Each high point on a tone wheel is called a tooth. The
number of teeth on each of these tone or phonic wheels, in conjunction
with the speed at which the tone wheel is revolving, determines the frequency
of the tone generated.
Each driving gear, with its two bakelite gears and four tone wheels, runs in a
separate compartment magnetically shielded from the rest by steel plates which
divide the generator into a series of bins.
All four tone wheels in any one compartment run at the same speed. The
individual tone wheel shafts are mounted in bearings made of a special
porous bronze and each of these bearings is connected to the oiling system
by a cotton thread from the oil trough. Thus, oil from the trough is carried
by capillary action to all bearings, penetrating them and lubricating the
actual bearing surface. The drive shaft and both motors are lubricated in
a similar manner. It is very important to use the recommended grade of
oil regularly, as it is essential to the proper operation of the organ that the
generator be well lubricated. If oil of varying grades is used, it is likely
that the generator may be sluggish in starting, and in time the threads may
gum up and prevent the proper flow of oil.
The two spring couplings on the motor shaft, the flexible couplings
between sections of the drive shaft, and the tone wheel spring couplings
all contribute to absorbing variations in motor speed. The synchronous
motor does not deliver absolutely steady power, but rather operates
with a series of pulsations, one with each half cycle. If the tone wheels
were rigidly coupled to the motor, this slight irregularity would carry
extra frequencies into each tone wheel. In addition, hunting is suppressed
by the resilient couplings and inertia members of the synchronous motor
proper.
Associated with each tone wheel is a magnetized rod about 1/4 of an inch
in diameter and 4 inches in length, with a coil of wire wound near one end
(See figure 3). The tip of the magnet at the coil end is ground to a sharp
edge and mounted near the edge of the tone wheel. Each time a tooth passes
this rod it causes a change in the magnetic field which induces a small
voltage in the coil, the frequency being determined by the number of teeth
and the wheel speed.
Small coils are used on the higher frequency magnets and larger coils
on the lower frequencies. It is found that large pole pieces are needed on
the low frequency magnets to give good frequency output, but it is necessary
to use smaller ones on the high frequencies to prevent excessive iron losses.
2
Some of the coils have copper rings mounted on them for the purpose of
reducing harmonics. As these are used only on fairly low frequency coils,
the eddy current loss in such a ring is small for the fundamental frequency
of that coil, but high for its harmonics. This has the effect of reducing
the relative intensities of any harmonics which may be produced by irregularities
in the tone wheels. The wheels are cut so to give as nearly
a sine wave as possible, but the generated voltage seldom reaches that ideal
condition, since even a change in the air gap will change the wave form. The
tip of each magnet, as well as the edge of each tone wheel, is coated with
lacquer to prevent corrosion. For, should oxidation set in, the change in
tooth shape would introduce irregular frequencies.
Locations of the various magnet and coil assemblies are shown in figure 4.
They are identified by their frequency numbers, and the broken line between
any two numbers indicates that these two frequencies are supplied by one
tone wheel assembly.
Each magnet is set at the factory with the set screw partially loosened,
while observing an output meter. Experience has shown that the magnets
seldom need adjustment and that setting them without proper equipment involves
danger of damaging both magnet and wheel. Therefore it is not recommended that
the service man attempt this adjustment.
As a means of eliminating any vagrant harmonics that may be present, there
are filters consisting of small transformers and condensers associated with
certain frequencies. The transformers have a single tapped winding, and this
tap is grounded, so one side, which is connected to the corresponding magnet
coil through a condenser, forms a resonant circuit for the fundamental frequency of
that coil. This tends to emphasize the fundamental and suppress
harmonics.
Locations of these transformers are shown in figures 5 and 6.
These transformers and condensers are mounted on the top of the
generator assembly. The transformers are mounted at an angle, thus
minimizing interference between them. The cores of the transformers
are made of a special iron, and the number of laminations used is adjusted
to secure the proper inductance. Wires from the magnet coils connect to
the transformers, and wires from the transformers lead to the terminal
strip on the generator.
This terminal strip carries the output frequencies of the generator, which
are arbitrarily numbered from 1 to 91 in order of increasing frequency.
This frequency numbering is continued throughout the instrument. In some
models the frequencies are not in order on the terminal strip, and figures
5 and 6 indicate the arrangement for different models. Several terminals
at the right end are grounded to the generator frame and serve to ground
the manuals and pedals.
3
Transformers and condensers are not used below frequency 44, but a
length of resistance wire shunts each generator. Frequencies 44 to 48
have transformers only, while both transformers and condensers are used
for frequencies 49 to 91 except in the case of Model A consoles numbered
below 2179, which do not have condensers for frequencies 49 to 54 inclusive.
Two condenser values are used: 0.255 mfd for frequencies 49 to 54, and
0. 105 mfd for frequencies 55 to 91. The transformers are all different.
Each transformer is matched to its condenser and any replacements are
supplied as matched pairs by the factory.
There are several types of generators in use and the following information
will aid the service technician in identifying the console on which work is
being performed.
91 Frequency Generator:
Model A serial No. 1 - 2676 Model D serial No. 1 - 3143
Model B serial No. 4000 - 10549 Model E serial No. 8000 - 8663
Model C serial No. 1 - 1247
The number of tone wheels on the above models is 91, and 5 blank wheels
are used to maintain the balance of the rotating units. There are twelve
wheels with two teeth, one to operate at each of twelve speeds, and
similarly twelve have four teeth, twelve have eight teeth, twelve have
sixteen, twelve have thirty-two, twelve have sixty-four, twelve have one hundred and
twenty-eight and seven have one hundred ninety-two. An assembly with a two-tooth
wheel also has a thirty-two tooth wheel which generates a frequency four octaves
above the other. The four and sixty-four tooth wheels go together, as do the eight
and one hundred twenty-eight tooth wheels. The twelve sixteen tooth wheels are
mounted with seven one hundred ninety-two tooth wheels and the five blank wheels. In
this last group the high frequency is not four octaves above, but is four octaves
less five semi-tones above the lower.
This arrangement gives a total of 91 frequencies that are connected to
corresponding terminals on the generator, and then to the manuals and
pedal switch. In all cases, as mentioned above, the generator must be
used with corresponding manuals and pedal switches and other types of
generators cannot be substituted.
82 Frequency Generator:
Model A serial No. 2677 - 2711 Model D serial No. 3144 - 17,074
Model B serial No. 10, 550 - 17, 074 Model E serial No. 8664 - 8739
Model C serial No. 1248 - 17, 074 Model G serial No. 4101 - 7349
In the above consoles, frequencies # 1 to 9 have been omitted from the
generator, and only 82 generator terminals are used. Similarly, there are
only 82 tone wheels and magnets in the generator instead of 91. Blank wheels
replace the nine two-tooth tone wheels formerly used to produce frequencies
1 to 9.
4
This generator change accompanies a wiring revision in the manual and pedal
switches which makes the frequencies from 1 to 9 unnecessary. Generators
having but 82 frequencies are easily identified by a blank space on the terminal
strip at the left of the ground terminals. The first terminal at the left of this
space is terminal # 10.
91 Frequency Generator with Complex Tone Wheels:
Model BV serial No. 17075
Model CV serial No. 17075
Model R T serial No. 1001
Model B-2 serial No. 35000
Model C~2 serial No. 35001
Model RT-2 serial No. 1300
- 29737
- 30287
- 1201
- 40303
- 40459
- 2150
In these consoles, the original two-tooth wheels in the generator have been
replaced with twelve two-tooth complex tone wheels, which supply a fundamental
tone, that is enriched with the odd-number harmonics. Both manuals
and pedal switch are wired differently and are therefore not interchangeable
with earlier models.
91 Frequency Generator with Complex Tone Wheels and narrow cover:
Models B-2, C-2, RT-2 (Except those listed in prior paragraph) and all
B-3, C-3, RT-3, A-100, and D-100.
This generator has twelve complex tone wheels and is identical to the one
above except for the generator cover. Because the output terminals of this
cover are not in order of frequency (See figure 6) this type of generator is
not interchangeable with the one above.
Note : Consoles have been made equipped with 115 volt 25 or 50 or 60 cycle and
230 volt 50 or 60 cycle generators. If the owner is contemplating moving to a
location having a different frequency of current, the complete generator must
be changed. Where voltage changes only are encountered, step-up or step-down
transformers will be necessary.
Generator Anchoring
When a console is set up for operation the anchoring must be loosened so that
the generator will float freely on its spring suspension system. No damage
will result if this is not done, but the console will sound noisy, and the same
is true if the anchoring is loosened but the console is not level. If the console
is to be moved a long distance the anchoring should be tightened during such
moves.
Several different types of anchoring have been employed and instructions for
loosening and tightening the generator in any particular console are given on
the instruction card contained in the bench which accompanied that console.
5
TEPICAL FILTER CONNECTIONS
Figure 1
6
TONE. WHEELS
TONE GENERATOR
Figure 3.
FRONT VIEW OF MAIN GENERATOR
GENERATOR MAGNET LOCATIONS
Figure 4.
(Numbers shown are frequency numbers)
7
SYNCHRONOUS
MOTOR END
NUMBERS ON FILTER TRANSFORMERS ARE FREQUENCY NUMBERS
OF TRANSFORMERS
STARTING
MOTOR END
H.<Z<Z<Z ^<2.<Z^><Z^> U ^<2.<2<Z ^<z<z<z
)ooooooooooooo oto ooooaooooooooooojoaooo jfto oaoooojooooooooooooooo olio ooooooaaoofaao o~S
OUTPUT TERMINAL FREQUENCY NUMBERS '
IN CONSECUTIVE ORDER
FIGURE 5 -MAIN GENERATOR COVER
MOOELS A t B,BC,BV, C,CV,D,DV, E, AND RT
MODEL B-2 SERIAL NUMBERS BELOW 40204
MODEL C-2 SERIAL NUMBERS BELOW 40460
MODEL RT'2 SERIAL NUMBERS BELOW 2lSl
NUMBERS ON FILTER TRANSFORMERS ARE FREQUENCY NUMBERS
OF TRANSFORMERS
FILTER TRANSFORMERS
SOME GENERATORS HAVE FILTER CONDENSERS
MOUNTED ON TOP OF TRANSFORMERS
OUTPUT TERMINAL FREQUENCY NUMBERS'"
FIGURE 6 - MAIN GENERATOR COVER
MODEL B-2 SERIAL NUMBER 40304 AND ABOVE
MOOEL C-2 SERIAL NUMBER 4O4E0 ANO ABOVE
MODEL RT-2 SERIAL NUMBER 2151 AND ABOVE
ALL B-3 C-3 AND RT-5 CONSOLES
THE HAMMOND ORGAN
- 6 -
CHORUS GENERATOR
HAMMOND ORGAN COMPANY
North Western Avenue - Chicago
Diversey Ave - Chicago
North 25 th Avenue - Melrose Park
Copenhagen Court - Franklin Park
Illinois
USA
CHORUS GENERATOR
(Used in Models BC, D, E, and G)
The purpose of the chorus generator is to add a series of slightly sharp and
slightly flat tones to the true tones produced by the main generator. The resulting
electrical wave contains a complex series of undulations which enhance the pleasing
effect of many tone qualities, notably string and full organ combinations. It should
be noted that no chorus effect is produced on frequencies below 56.
The frequencies covered by the chorus generator are numbers 56 to 91 inclusive on
the main generator. The difference in frequency between the main generator and
either flat or sharp tone is 0. 8% for frequencies 56 to 67 and 0. 4% for frequencies
68 to 91. It is necessary that a lesser percentage of frequency difference be
present in the higher register in order to avoid too rapid undulation.
The chorus generator assembly, like the main generator, has a drive shaft with
twenty-four brass gears. Each gear drives a single assembly consisting of two tone
wheels. The drive gears vary as to the number of teeth, and the tone wheels operate
at twenty-four different speeds. This generator has forty-eight tone wheels, each
with a separate magnet and pick-up coil. Of these tone wheels, twenty-four are
single and twenty-four are double (see figure 1). The double tone wheels consist of
two discs with different numbers of teeth mounted on one brass hub. The single
wheels are electrically connected in pairs, each pair being so connected as to have
the same effect as one double wheel.
Figure 2 is a complete wiring diagram for connections between main and chorus
generators, and figure 3 is a back view of the chorus generator indicating the
frequency number of each magnet.
Figure 1 .
1
CABLE CONNECTIONS
TO CHORUS GENERATOR
Figure 2.
73
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2 I
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BACK VIEW OF CHORUS GENERATOR
( NUMBERS SHOWN ARE FREQUENCY NUMBERS)
CHORUS GENERATOR MAGNET LOCATIONS
Figure 3
2
START MOTOR start motor P* START MOTOR END
Figure 5 (there is no figure 4 - JL) below shows the signal flow between both Main
and Chorus Generator:
CHORDS GENERATOR WIRING
FIGURE 5.
3
THE HAMMOND ORGAN
-7-
CONSOLE POWER WIRING
HAMMOND ORGAN COMPANY
North Western Avenue - Chicago
Diversey Ave - Chicago
North 25 th Avenue - Melrose Park
Copenhagen Court - Franklin Park
Illinois
USA
CONSOLE POWER WIRING
(Main and Chorus Generators)
Starting and Synchronous Motors
A shaded pole induction motor is used for starting the generator and is located at
the right end of the generator as viewed from the back. The rotor of this motor will
slide endwise when current is supplied and engage a pinion on its shaft with a gear
on the generator driving shaft, bringing the tone generator up to slightly greater
than synchronous speed.
When the organ is started, the starting switch is turned on and held for about 8
seconds while the starting motor brings the system up to speed. The run switch is
then turned on. This switch simultaneously connects the synchronous motor and
introduces a resistor in series with the starting motor (figure 1), thus reducing
its driving power. With a braking action of the synchronous motor and a loss of
power of the starting motor, the system slows to synchronous speed and the
synchronous motor begins to carry the load. A period of about 8 seconds should be
allowed for this to take place, after which the starting switch may be released. The
starting switch springs back to the off position, and turns off the starting motor,
which is disengaged from the rotating shaft by a spring.
It should be noted that the synchronous motor can supply power only at synchronous
speed. Therefore, if for any reason the system fails to reach synchronous speed it
will not continue to run after the starting switch is released. Failure to start
properly is usually due to increased oil viscosity and may be overcome by an
increase in starting time.
As the schematic diagram (figure 1) indicates, the run switch in its off position
shorts out the wirewound resistor attached to the line panel. If the run switch is
defective in its off position, the generator will not start because this resistor
will be permanently in series with the starting motor. Before assuming that there is
anything amiss with the motors, short out this resistor and start the generator in
the normal manner. If the generator operates satisfactorily, replace the run
switch.
The run switch on all consoles is a two-circuit switch, but types of switches
having two different terminal arrangements have been used, as shown in figure 2.
When replacing a switch, observe the wiring of the old switch and check the
connections of the new switch with an ohmmeter. Note that black and blue are
connected in the on position, and yellow and brown are connected in the off
position, no matter which type of switch is used.
1
2
FIGURE 1
SWITCH AND MOTOR CIRCUITS
BLACK BLUE BROWN I BLACK
O
3 « .
Q JU
W W ft
CO Q W
D o »
~ ft ^
^ < •
CO J CQ
3
FIG 2
TWO TYPES OF "RUN" SWITCHES
4
LINE PANEL (EARLY CONSOLES)
S
Uh
5
LINE PANEL (LATER CONSOLES)
THE HAMMOND ORGAN
- 8 -
MANUALS, PEDALS,
MATCHING TRANSFORMERS
and
PRESET PANEL
|l'i|l | i|
HAMMOND ORGAN COMPANY
North Western Avenue - Chicago
Diversey Ave - Chicago
North 25 th Avenue - Melrose Park
Copenhagen Court - Franklin Park
Illinois
USA
Figure 1: Typical Console Manual (B2)
For a description of controls - see Section 2
Manual Chassis Assembly - Models A, AB, AV, BC, BCV, BV, C, CV, D, DV,
G, GV, RT.
The manual chassis assembly, figure 1, which includes the upper and lower
manuals and the preset panel, has a terminal strip under each manual made
up of 82 or 91 terminals, depending on the generator being used, to
accommodate the frequencies from the tone generator assembly. Each manual
has 61 playing keys, 9 preset keys, and 2 adjust keys, each of which operates
nine small bronze contact springs with precious metal points (See figure 2).
When a key is pressed these points make contact with nine busbars extending
the entire length of the manual. The busbars also have precious metal contact
surfaces.
The nine contact springs under each key carry the nine harmonics of the
particular note with which they are associated (See figure 3) and are
connected by resistance wires to the proper terminals on the terminal
strip. Therefore all key contacts are alive whenever the generator is
running. See schematic diagram of console in the Diagrams & Schematics section.
1
ACTUATOR FOR ONE KEY
1
8TH HARMONIC !
1 /
6TH HARMONIC i j IK
5TH HARMONIC !
i o
4TH HARMONIC \
: o
1
3RD HARMONIC !
i o
2ND HARMONIC
i o
FUNDAMENTAL 1
! I)
SUB 3RD HARMONIC i
i A
SUB FUNDAMENTAL |
1 i
1 ' ft
' ! ft-*-
TOP CONTACT SPRING
TOP BUSBAR
BOTTOM CONTACT SPRING
BOTTOM BUSBAR
ARRANGEMENT OF MANUAL CONTACTS
Figure 3
When a playing key is pressed, its nine frequencies are impressed on the nine
busbars of the manual. As there are no wires connected to these busbars, a preset or
adjust key must be depressed before any circuit can be completed. Each preset and
adjust key has nine contacts exactly like those of the playing keys. These keys have
a locking and trip mechanism which allows only one key to be in operation at one
time. The key at the extreme left end of the manual is a cancel key, with no
contacts, which releases any preset or adjust key that happens to be depressed.
The adjust keys, A# and B, are connected by flexible wires, color-coded for easy
identification, to the corresponding nine drawbars. The drawbars slide over nine
busses which are connected to taps on the matching transformer. These correspond to
different intensities of sound as shown by numbers on the drawbars.
The two left groups of drawbars are associated with the upper manual, while the two
right groups work in conjunction with the lower manual. In each case the A# adjust
key controls the left hand group of drawbars for that manual. The nine preset keys,
from C# to A inclusive, are wired to flexible leads terminating at the preset panel
in the back of the console, where the various tone colors are set up by connecting
each wire to a screw terminal corresponding to the desired intensity of the
harmonic. These screw terminals are located on 9 horizontal bars, each representing
a certain intensity for all wires attached to that bar.
The drawbar busses and the preset panel bars are connected in parallel to taps on
the primary of the matching transformer.
2
Manual Chassis Assembly - Models B~2, C~2 and RT~2
In these selective vibrato consoles, the individual manuals are the same as in other
models but the drawbar assembly is different, having three tilting tablets (Vibrato
Swell On-Off, Vibrato Great On-Off and Volume Soft-Normal) at the left of the
vibrato switch knob.
The selective vibrato feature requires that the preset panel and drawbar assembly be
divided and connected to two matching transformers, each serving one manual. See
Diagrams & Schematics section. The Great, or lower manual, matching transformer also
serves the pedal keyboard.
Continuous-contact drawbars are used in later consoles of this type. They operate
more smoothly and require less accuracy of adjustment than the earlier type having
nine definite positions or steps. Each one has two contacts connected together by a
one ohm resistor, so that at least one of the contacts touches some bus at all times
and there are no dead spots in the drawbar motion. The resistor avoids short-
circuiting adjacent busbars.
Manual Chassis Assembly - Models B~3, C~3, RT~3, A- 100 & D-100
The above description also applies to these models, but the start and run switches
are relocated to provide room for four tilting tablets which control the Percussion
feature, described in Section 2. All manual chassis assemblies are equipped with
continuous contact drawbars.
Manual Chassis Assembly - Model E
The appearance of the upper, or swell manual, and the lower, or great manual, is the
same as on other models except that numbered pistons are used instead of preset
keys. These pistons operate in exactly the same manner, and produce the same
effects, as do the preset keys on the other models.
The internal wiring of the manuals is to a large extent the same as in other models,
but the use of two tremulants requires that the preset panel and drawbar assembly be
divided, and that two matching transformers be used, each manual being connected to
its own matching transformer.
Manual Busbar Shifters
The precious metal contact surfaces of the key contacts and busbars are not subject
to corrosion, and the manuals are sealed to exclude dust as far as possible. In
spite of these precautions an occasional particle of dust many lodge on a contact
and cause the note to be scratchy, noisy, or silent, and for this reason a busbar
shifting mechanism is provided on each manual to slide the busbars endwise and thus
provide a fresh contact surface. The busbar shifter for each manual is a slotted
stud near the right end of the manual as viewed from the back of the console (see
rear view of console in Section 2 for location).
If any note becomes scratchy or silent, it should first be struck 15 or 20
times in a rapid staccato manner to loosen the dirt. This will usually dislodge
the particles and clear the note.
3
In case this procedure is not effective, the busbar shifter for that manual may be
adjusted by turning the stud about two turns in either direction. It may sometimes
be necessary to hold down the offending key while turning the busbar shifter, in
order to wipe the contact clean.
Model A consoles below serial number 995 are not equipped with busbar shifters
except in cases where the manual chassis and pedal switch have been rebuilt.
Manual Wiring - Models A, AB, AV, BC, BCV, BV, C, CV, D, DV, G, GV, RT.
Figure 4, a wiring chart for the playing manuals, will be helpful in tracing
difficulties associated with the generator or manuals. All playing manuals are wired
alike from drawbar 2 to drawbar 8 inclusive, but the wiring of drawbars 1 and 9
varies. Column A shows the wiring of drawbar 1 for consoles above serial number
17075; column B refers to all consoles having 82 note generators; and column C is
the wiring used in all earlier consoles. Column D shows wiring of drawbar 9 for
Model A consoles below serial number 2500 and Model BC console below 5076; column E
refers to all later consoles.
These variations in wiring are designed to match the different type of generators
described in the section covering tone generators, and therefore the various types
are not interchangeable.
Manual Wiring - Models B~2, B~3, C~2, C~3, RT~2, RT~3, A-100 & D-100
The key circuit wiring for these models is the same as for previous consoles above
serial number 17075, and so columns A and E in figure 4 apply.
4
5
Figure 5: Typical 25 note pedal assembly
Pedal Switch Assembly - All Models with 25 Note Pedal Keyboard
The pedal switch (shown in figure 5) is similar in construction to the manuals
except that only four busbars are included instead of nine. Each of the 25 pedals
actuates a double set of contact springs, making eight contacts available for each
note. Each note consists of a fundamental and number of harmonics, no sub-harmonics
being used. The pedal contact springs are connected to terminals by resistance wires
similar to those used in the manual assembly, and a cable connects these terminals
through a wiring tube to the proper terminals on the generator terminal strip.
Four colored wires carry the pedal tones from the busbars to the pedal drawbars.
In some models the wires are connected first to a resistor panel on the back of the
manual assembly. A small choke coil and resistor mounted on the manual assembly are
wired to the lower drawbar (see figures 8, 9, 10, 11) and serve to filter out any
higher harmonics or transients which might be present in the lower pedal
frequencies.
Early consoles used only seven contacts on each pedal (see figure 6) and were
wired so that any harmonic would appear on only one pedal drawbar (figures
8 and 9). Later consoles use all eight contacts (figure 7) and employ a system for
mixing the 16 ft. and 8 ft. tones (figures 10 and 11). The harmonic arrangement of
the contacts is also different in these later units.
Figure 13 is a wiring chart for the pedals, showing the frequency numbers appearing
on each pedal contact. The variations in wiring make the pedal switches match the
different types of generators described in the section covering tone generators, and
therefore the various types are not interchangeable.
Specific pedal wiring of any console can be determined by obtaining the serial
number and referring to figures 8 to 11. Included in these sketches are references
to figure 13 wiring chart.
6
ONE PEDAL
6TH HARMONIC
TOP CONTACT SPRIN GS
- 8TH HARMONIC
4TH HARMONIC
5TH HARMONIC
2ND HARMONIC
3RD HARMONIC
FUNDAMENTAL
NOT CONNECTED
^ BOTTOM BUSBAR
ARRANGEMENT OF PEDAL CONTACTS
MODEL A CONSOLES SERIAL NOS. 1 To 2499
MODEL B AND BC CONSOLES SERIAL NOS. 4000 To 5075
ONE PEDAL
TOP CONTACT SPRINGS
10TH HARMONIC-
12TH HARMONIC
6TH HARMONIC
2ND HARMONIC
FUNDAMENTAL
8TH HARMONIC
4TH HARMONIC
3RD HARMONIC
BOTTOM BUSBAR
ARRANGEMENT OF PEDAL CONTACTS
ALL OTHER CONSOLES WITH 25 PEDALS
7
IOTH i 12 TH HARMONICS
2ND PEDAL DRAWBAR
FIGURE 8 PEDAL CIRCUITS
MODEL A CONSOLES SERIAL NO. I TO 2499
MODEL B AND BC CONSOLES SERIAL NO. 4000 TO 5075
(FOR PEDAL WIRING SEE FIGURE 13, COLUMNS l,4,5,6,7,8,9)
FIGURE 9 PEDAL CIRCUITS
MODEL A CONSOLES SERIAL NO. 2500 TO 2676
MODEL B AND BC CONSOLES SERIAL NO. 5076 TO 10549
MODEL BA(PLAYER)CONSOLES-ALL
MODEL C CONSOLES SERIAL NO. 1200 TO 1247
MODEL D CONSOLES SERIAL NO. I TO 3143
(FOR PEDAL WIRING SEE FIGURE 13, COLUMNS 1,4,5,6,8,9,10,1 Q
8
FIGURE 10 PEDAL CIRCUITS
MODEL A CONSOLES SERIAL NO. 2677 TO 2711
MODEL B, BC, AND BV CONSOLES SERIAL NO. 10550 TO 17074
MODEL C AND CV CONSOLES SERIAL NO. 124 8 TO 17074
MODEL D AND DV CONSOLES SERIAL NO. 3144 TO 17074
MODEL G CONSOLES -ALL
RESISTOR PANEL
FIGURE II PEDAL CIRCUITS
MODEL BV AND CV CONSOLES SERIAL NO. 17075 TO 30287
MODEL RT CONSOLES SERIAL NO. 1001 TO 1201
MODEL B-2 AND C-2 CONSOLES SERIAL NO. 35000 AND ABOVE
MODEL B-3 AND C-3 CONSOLES SERIAL NO. 56000 AND ABOVE
MODEL RT-2 CONSOLES SERIAL NO. 1300 AND ABOVE
MODEL RT-3 CONSOLES SERIAL NO. 4000 AND ABOVE
(FOR PEDAL WIRING SEE FIGURE 13, COLUMNS 1,2,4,6,8,9,10,11)
9
2 TO INDICATOR
3
4 LIGHTS
10
WIRING OF PEDAL CIRCUITS
SIGNAL
BUSBAR , PICKUPS PEDAL
t
DOWN STOP
FELT
Figure 21: Concert style, 32 note pedal assembly
Pedal Switch Assembly - RT, RT~2, RT~3, and D-100
The pedal switch (shown in figure 21) is similar in internal construction to the
manuals (figure 22). Each of the 32 pedals actuates a set of contact springs,
making nine contacts available for each note. Each note consists of a fundamental
and a number of harmonics, no sub-harmonics being used. The pedal contact springs
are connected to terminals by resistance wires similar to those used in the manual
assembly, and a cable connects these terminals to the proper terminals on the
generator terminal strip. Only seven contacts are used for the mechanical generator
notes, the other two contacts are used by the pedal solo unit as explained later in
this book.
Four colored wires carry the pedal tones from the busbars to the pedal drawbars.
The wires are connected first to a resistor panel on the back of the manual
assembly. A small choke coil and resistor mounted on the manual assembly are wired
to the lower drawbar (see figure 23) and serve to filter out any higher harmonics or
transients which might be present in the lower pedal frequencies.
Figure 24 is a wiring chart for the pedals, showing the frequency numbers appearing
on each pedal contact.
Pedal Switch Assembly - Model E
Nine busbars are used in the Model E pedal switch assembly. Figure 12 illustrates
the arrangement of these busbars and the nine contact springs of a typical pedal
key. There are 32 pedal keys, and four pedal toe pistons. These pedal toe pistons,
which correspond to the preset pistons of the manuals, also have nine contact
springs touching the same nine busbars and have a locking arrangement by which only
one piston remains in operation at one time.
11
Frequencies impressed on the busbars, when a pedal is played, are picked up by the
contacts of the pedal piston which is in use, and go from there to the preset panel
through pistons 1 or 2 or to the drawbars through piston 4. From the coupler (Piston
3) the upper seven harmonics connect to busbars in the great manual, while the lower
two connect to the lower pedal drawbar and permit it to be used with the coupler.
Connections from the pedals to the manual are indicated in Figure 12. A low voltage
line from the preamplifier heater transformer operates the 2. 5 volt pedal preset
indicator lamps through the external contacts on the pedal switch. Several filter
chokes and resistors mounted on the pedal switch are wired in series with leads from
the lower pedal harmonics.
ACTUATOR FOR ONE KEY
7
TUNING
iiX
KEYING
(h —
- TOP BUSBAR
FUNDAMENTAL
T
2ND, 3RD HARMONIC
0
2ND HARMONIC
i i
T"
4TH HARMONIC
T
6TH HARMONIC
T
8TH HARMONIC
i i
i
10TH HARMONIC
T"
i i
u
#-« —
_ BOTTOM BUSBAR
ARRANGEMENTS OF PEDAL BUSSES
D-100
SERIES
FIGURE 22
FIGURE 23
12
Pedal
No.
6
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
Note
Fund
2nd and
3rd Harm.
2nd Harm.
4th Harm.
6th Harm.
8th Harm.
10th Harm.
C
13
13
25
32
41
c#
14
14
26
33
42
D
15
15
27
34
43
D#
16
16
28
35
40
44
E
5
17
17
29
36
41
45
F
6
18
18
30
37
42
46
19
19
31
38
43
47
a
20
32
39
44
48
o
•H
21
33
40
45
49
o
22
34
41
46
50
A#
23
35
42
47
51
B
o
o
24
36
43
48
52
C
13
32
25
44
49
53
C#
14
33
26
45
50
54
D
15
34
27
46
51
55
D#
16
35
28
40
47
52
56
E
17
36
29
41
48
53
57
18
37
30
42
49
54
58
19
3b
31
43
50
55
59
G
20
39
32
44
51
56
60
G#
21
40
33
45
52
57
61
A
22
41
34
46
53
58
62
A#
23
42
35
47
54
59
63
B
24
43
36
48
55
60
64
C
25
44
37
49
56
61
65
C#
26
45
38
50
57
62
66
D
27
46
39
51
58
63
67
D#
28
47
52
59
64
68
E
29
48
41
53
60
65
69
F
30
49
42
54
61
66
70
F#
31
50
43
55
62
67
71
G
32
51
44
56
63
68
b
72
Frequency Number
FREQUENCIES USED IN PEDAL SWITCH
FIGURE 24
13
Pedal Switch Busbar Shifters
The pedal switch is equipped with busbar shifters similar to those on the manuals.
The pedal busbar shifter is a slotted stud on the rear surface of the pedal switch,
near the right end as you look in at the back. It should be adjusted as described
under Manual Busbar Shifters on page 3 of this section.
Pedalclavier
Pedal keys are set at the factory for average tension, but a re adjustable to fit
the requirements of the individual organist. Adjustment is accomplished by removal
of the top cover at the back of the pedal keyboard and setting the tension as
desired.
PEDAL
SWITCH
PUSHERS
TENSION
ADJUSTING
NUTS
PUSHER
ADJUSTING
NUTS
PEDAL
KEYBOARD
PEDAL
COVER
SINGLE
PEDAL
FIGURE 25
14
Pedals 26 to 32 used in Model E, RT, RT-2, RT-3 and D-100 only
For Harmonics Used In a Given Console See Fig. 8-9-10-11-12.
FREQUENCIES USED IN PEDAL SWITCHES
Figure 13
15
Pedal Busbar Shifters
Pedal switches in all consoles (except Model A consoles below serial number
995) are equipped with busbar shifters similar to those on the manuals. The pedal
busbar shifter is a slotted stud on the rear surface of the pedal switch, near the
left end as you look in at the back. It should be adjusted as described under Manual
Busbar Shifters on page 3 of this section.
Pedal Keyboard
Pedal keys are set at the factory for average tension, but are adjustable to fit the
requirements of the individual organist. Adjustment is accomplished by removal of
the top cover at the back of the pedal keyboard and setting the tension nuts as
desired.
SWITCH PUSHER
Ul
1
1:1
m
m
blip!
fSlII&l
TENSION AD
KEYBOARD
gure 14
6
Preset Panel - Models A, AB, BC, BCV, BV, C, CV, D, DV, G. GV, RT
The tone signals from the preset keys on both manuals are carried by color-coded
wires to the preset panel in the back of the console.
The preset panel is a set of nine bars, wired to the taps on the matching
transformer, corresponding to different intensities of sound as shown by numbers
stamped on the bars. Each preset wire, carrying a single harmonic, is fastened under
a screw on the bar which represents the desired intensity of that harmonic. This is
equivalent to setting a harmonic drawbar to the corresponding number.
Preset combinations may be changed at will by removing the console back and
following the directions on a card inside. This card is reproduced below (figure
15).
Directions for Making Pre-Set Panel Connections
There are 9 color-coded wires threaded through one of the lower holes for each pre-set key. Above each hole are 9 binding posts arranged
in vertical order, and above the uppermost binding post is a name plate specifying the pre-set key associated with the row of wires below.
The lowest binding post is that of zero strength and corresponds to a harmonic control pushed all the way in. The uppermost binding
post is of 8 strength and corresponds to a harmonic control drawn all the way out. The bus-bar strips for each level are extended to the
left where they are marked with their appropriate strength numbers.
For example, suppose the combination 006523411 is to be set up on the D# of the
upper manual. It will be found helpful, especially when setting several combina-
tions, to use the following chart:—
Manual
Key
Brown
Red
Orange
Y ellow
Green
Blue ,
Violet
Grey
White
•Upper
D#
0
0
6
5
2
3
4
i
1
Color Code Explanation
Each group of 9 wires is color-coded as follows:
Sub-fundamental ( brown drawbar ) brown wire
Sub-3rd harmonic (brown drawbar) red wire
Fundamental ( white drawbar ) orange wire
2nd Harmonic ( white drawbar ) yellow wire
3rd Harmonic ( black drawbar ) green wire
4th Harmonic (white drawbar) blue wire
5th Harmonic ( black drawbar ) violet wire
6th Harmonic (black drawbar) grey wire
8th Harmonic (white drawbar) white wire
With a screw driver remove the connections already made on the D# "Upper Manual” row of binding posts and separate the 9 wires
from each other. Referring to the chart above, the brown and red wires arc twisted together and connected with the binding post on the
level marked "O” (lowest level). Next, the white and grey wires are twisted together and inserted under the binding post on the level
marked "1.” Similarly, the green wire is connected on level “2,” the blue wire on level "3,” the violet wire on level “4,” the yellow
wire on level “5,” and the orange wire on level “6.” The wire used for the pre-set connections is standard “push-back” wire. The
insulation is loose and should be pushed back to expose the desired length of bare wire. Never remove the insulation by shinning with
pliers or a knife. After a connection has been made, push the insulation forward with the fingers as far as it will go. Be sure to twist the
wires together so that there will be no stray strands connecting one bar with any other bar. The binding posts should be firmly tightened
over the wires to insure good electrical contacts. PO-2963-1
Figure 15
Preset Panel - Models B~2, B~3, C~2, C~3, RT~2, RT~3, E, A-100, D-100
In these models the preset panel is divided into two sets of nine bars, each
connected to a separate matching transformer. One set is used for the swell (upper)
manual, and the other for the great (lower) manual and pedals. The preset panel on
Model E is slightly longer than on the other models to accommodate the two pedal
presets.
17
Matching Transformers
The matching transformer is used to match the low impedance of the generator and key
circuits to the high impedance amplifier input. It serves also, through taps on its
primary winding, to establish a series of intensity levels for the drawbars and
preset panel.
The following types of matching transformers have been used. In most cases they are
not interchangeable, and console serial numbers should be furnished when ordering
replacements.
1. Large-core transformer, used in Models A, B, BA, BC, C, D, and G. These were
enclosed in two sizes of shield cans at various times, but they are identical
otherwise. Two transformers of this type were used in Model E.
2. Large-core transformer with taps revised. Matching transformers in organs with
non-selective vibrato (Models BV, BCV, CV, DV, and RT) are slightly different from
earlier models in the number of turns to the first three taps. If a transformer in
an earlier organ is replaced by one of the newer type, any preset wires on preset
panel bars 1, 2, and 3 should be set to the next higher bar in order to make the
combination sound the same as before. For instance, combination 00 3543 111 with
the old type transformer would become 00 4544 222 with the new one.
3. Small-core transformers used in selective vibrato organs Models B-2, C~2, and RT-2
having preamplifiers code A, B and C. Two transformers are used in each organ, one
with large stack for the upper or swell manual, one with small stack for the lower
or great manual and pedals.
4. Revised small-core transformers with smaller stack and greater number of turns.
These are used in B-2 consoles serial number 42636 and above, C~2 consoles serial
number 42875 and above, and RT-2 consoles serial number 2381 and above (having
preamplifiers code D, E, F, G) and in B-3, C~3, RT-3, A-100 and D-100 consoles.
Because differences in the preamplifier input circuits will cause irregular
response, these transformers are not interchangeable with the previous type, unless
the preamplifier is changed at the same time.
OPERATION OF MECHANISM ON PRESET KEYS
In their basic construction the preset keys are identical to the playing keys.
Each has a plastic key mounted on a metal channel, pivoted in the rear and with a
guide toward the front to minimize side motion.
On the front edge of each channel of the 9 preset keys and 2 adjust keys, two flat
springs are attached, one 5/8^ long of rather stiff material, and another
approximately 3 / 4 " long of softer material. The softer long spring is sandwiched on
top of the stUf spring, nearest to the key. The cancel key has only one heavy spring
approximately 1 " long.
18
When a preset key is depressed, the longer soft spring is forced downward and snaps
under a tubular rod which is part of the cradle. The cradle is constructed of two
tubes approximately 6- long and assembled 3/4 - apart. One tube is used as a
fulcrum, the entire assembly being mounted perpendicular to the preset keys. A
spring and bumper hold the cradle at a 60 degree angle toward the front of the
console.
Once a key has been depressed, the soft spring remains under the tube. It is backed
by the short stiff spring to give it sufficient tension to hold the key down. When
the next preset key is depressed, the cradle is forced down and outward, permitting
the previously actuated key to come up, but again locking the one last depressed.
If two preset keys are depressed at once, both will lock down. The cancel key with
its long stiff spring is then used and forces the cradle down, causing all preset
keys depressed to return to their normal position. As there is no locking spring on
the cancel key, it will immediately return to its normal position.
PRESET CRADLE RETURN SPRING
Earlier instruments had coil springs of various types to perform the function of
returning the cradle assembly to its rest position, and replacement, when necessary,
became rather involved.
A more durable spring has been devised, and is used on the later instruments.
It can also be used for servicing the earlier consoles.
Replacement is made as follows: If it is determined that a new return spring is
necessary, on either manual, the left hand end block of the manual needing the
replacement should be removed. The upper or lower manual assembly will have to be
raised to gain access to the wood screws holding this block. After removal of this
block, the end of the cradle assembly will be visible. Also visible will be the stop
felt and bracket assembly. This is a small angular bracket with a small piece of
felt rivited to it, mounted in a vertical position. Remove and discard this part.
Install the new assembly so that the felt pad is above the preset cradle, and the
flat spring is below the cradle, as shown in figure 16. Clamp it in the center of
the range of adjustment provided by the slot. Check all preset keys for operation,
and adjust the position of the new assembly in case any keys do not operate
correctly.
19
Figure 16
20
THE HAMMOND ORGAN
-9-
TREMULANT
&
RHEOSTAT BOX
|l'i|l | i|
HAMMOND ORGAN COMPANY
North Western Avenue - Chicago
Diversey Ave - Chicago
North 25 th Avenue - Melrose Park
Copenhagen Court - Franklin Park
Illinois
USA
TREMULANT SWITCH & CONTROL
MODELS A, AB, BC, C, D, G
The tremulant sometimes called tremolo, is a periodic loudness variation, or change
in intensity, which occurs at a constant frequency. It is fundamentally different
from the vibrato effect, which is created by a periodic raising and lowering of
pitch.
In the Hammond Organ, the tremulant effect is produced and controlled principally by
two components: the tremulant switch and the tremulant control.
The tremulant switch, mounted on the synchronous motor at the extreme left end of
the tone generator, is in effect a variable resistor with no sliding or rubbing
contacts. It consists of an eccentric, geared to the motor shaft, which advances a
laminated bakelite strip so as to alternately make and break 6 contacts in order.
Five resistors are connected to these contacts, ranging in value from 15, 000 to
450,000 ohms, together with a length of copper wire of very little resistance. At
one extreme position of the eccentric all contacts are broken and the circuit is
open. At the other extreme all contacts are closed and there is practically no
resistance in the circuit.
The tremulant control, a 130, 000 ohm variable resistor mounted on the manual chassis
assembly, is in parallel with the tremulant switch. When this control is turned to a
position of no resistance, the tremulant switch is shorted out. Conversely, when the
control is turned to its maximum resistance, the movement of the eccentric varies
the resistance of the circuit periodically from 0 to 130,000 ohms. This parallel
circuit is in series with the signal from the console, ahead of the pre-amplifier.
Therefore, the signal is varied during each revolution of the eccentric by an amount
depending upon the adjustment of the tremulant control. The tremulant system is not
used in console models having vibrato.
Concert Model E
The tremulant system for Model E organ is the same as that on other models except
that two switches are used. Each switch is mounted on one of the two synchronous
motors that are a part of the main generator and chorus generator respectively, and
each one is connected to one manual. The switch mounted on the main generator
operates at 400 R. P. M. and is connected to the Great manual. The other switch
operates at 348 R. P. M. and is connected to the Swell manual. Two types of tremulant
switches have been supplied, namely, the cage type and the enclosed type. These are
mechanically interchangeable, but replacing the cage type with the enclosed type
does require a slight change in the circuit. In the enclosed type, the condenser
shown as C5 in figure 4 is incorporated within the metal housing. Therefore, the C5
located in the rheostat box is not required and the tremulant switch red wire may be
attached to terminal 6, 7, or 8.
1
RHEOSTAT BOX
The rheostat box contains the expression control rheostat and other components,
including some terminals associated with the tremulant system. Figures 1 to 8 show
various models of rheostat boxes and their circuits. The rheostat box is used only
in console models with tremulant and with non-selective vibrato .
The rheostat itself is actually a variable resistor with no sliding contacts. When
the expression pedal is advanced a bakelite cam moves down, opening in succession a
series of 32 contacts, tipped with precious metal. The contacts are connected to
fixed carbon resistors.
Resistor R2 in figures 2 and 4 forms a constant load on the matching transformer,
while R4 and C4 serve to attenuate the higher frequencies. R4 and C4 were not used
in Model A consoles below serial number 1231. The rheostat, in series with bass
compensating condenser C2, is across the signal line so that when its resistance is
least the volume is least. Condenser C5 avoids excessive tremolo on the lower bass
frequencies. It was not originally installed in Model A consoles below serial number
2311. C3 is a blocking condenser and R3 is a grid resistor for the first
preamplifier tube.
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9
FIGURE
SWELL TREM. SWITCH
(CHORUS)
10
FIGURE
THE HAMMOND ORGAN
- 10 -
VIBRATO
&
PERCUSSION
|l'i|l | i|
HAMMOND ORGAN COMPANY
North Western Avenue - Chicago
Diversey Ave - Chicago
North 25 th Avenue - Melrose Park
Copenhagen Court - Franklin Park
Illinois
USA
THE HAMMOND VIBRATO
Hammond Organ consoles equipped with vibrato differ from tremulant models in the
omission of the tremulant switch, tremulant control, and non-vibrato preamplifier,
and in the addition of the vibrato line box, scanner, vibrato switch, and vibrato
preamplifier. Three degrees of vibrato are available and also a different degree of
chorus or celeste effect with each of the three degrees of vibrato. Console models
with the suffix -2 in their model designation have the selective vibrato feature,
with tilting control tablets permitting the player to place the vibrato effect on
either manual or both.
A conversion kit is available for installation in most earlier consoles not having
the vibrato, but it does not incorporate the selective feature.
PRINCIPLE OF OPERATION
The vibrato effect is created by a periodic raising and lowering of pitch, and thus
is fundamentally different from a tremolo, or loudness variation. It is comparable
to the effect produced when a violinist moves his finger back and forth on a string
while playing. Varying the frequency while maintaining constant volume.
Figure 1 - FUNDAMENTAL DIAGRAM OF VIBRATO EQUIPMENT
The Hammond Organ vibrato equipment (see simplified block diagram figure 1) varies
the frequency of all tones by continuously shifting their phase. It includes a phase
shift network or electrical time delay line, composed of a number of low pass filter
sections, and a capacity type pickup or scanner which is motor driven so that it
scans back and forth along the line.
Electrical waves fed into the line are shifted in phase by each line section (the
amount per section being proportional to frequency), so that at any tap on the line
the phase is retarded relative to the previous tap.
The scanning pick-up traveling along the line will thus encounter waves increasingly
retarded in phase at each successive tap, and the signal it picks up will
continuously change in phase. The rate at which this phase shift occurs will depend
on how many line sections are scanned each second.
1
Since a cycle is equivalent to 360 electrical degrees, a frequency shift of one
cycle occurs for each 360 electrical degrees scanned per second. For example, if the
scanner passes over the line at such a rate that 3600 electrical degrees are scanned
each second, there will be a frequency change of 10 cycles.
For the widest vibrato, the whole line is scanned from beginning to end in about
1/14 second, and this rate of change of phase causes about 1 h decrease in
frequency. Note that the frequency remains constantly 1 Zi low as long as the moving
pick-up retards the phase at a constant rate.
Since the pick-up sweeps from start to end of the line and then back, it increases
the frequency by an equal percentage on its return trip, the average output
frequency remaining equal to the input frequency. The exact amount of frequency
shift depends not only on the amount of phase shift in the line but also on the
scanning rate. This rate, however, is constant because the scanner is driven by the
synchronous running motor of the organ.
The degree of vibrato (or amount of frequency shift) may be varied by a
switch (not shown in figure 1) which causes the whole line to be scanned for
#3 (wide) vibrato, about half of it for #2. and about one third for #1.
A vibrato chorus effect, similar to the effect of two or three slightly out-of-tune
frequencies mixed together, is obtained when the vibrato output signal is mixed with
a portion of signal without vibrato. For vibrato chorus, part of the incoming signal
appears across the vibrato line and the rest across a resistor in series with the
line. As the vibrato effect is applied to the part of the signal appearing across
the line but not to the part appearing across the resistor, the combination produces
a chorus effect. For normal vibrato, this resistor is short-circuited.
In selective vibrato consoles the vibrato effect can be applied to either
manual separately or to both at once.
CONSTRUCTION OF COMPONENTS
Figures 2 and 3 show different models of the vibrato line box. Each of the air core
inductance coils is connected with one or more condensers to form one filter
section.
Figure 4 shows the construction of a typical vibrato switch. Some models differ in
wiring and number of contacts, but all are similar in mechanical arrangement.
The scanner (figure 5) is mounted on the main generator synchronous motor and driven
at 412 revolutions per minute. It is a multi-pole variable condenser with 16 sets of
stationary plates and a rotor whose plates mesh with the stationary ones. In figure
5B two sets of plates have been removed to show the rotor.
Signals coming from the line through the vibrato switch appear on the stationary
plates and are picked up, one at a time, by the rotor. Connection to the rotor is
made by carbon brushes as shown in figure 5A. Two brushes touch the sides of the
contact pin and a third presses on the end, in order to eliminate the possibility
of contact failure.
2
21 Line Tap and Terminal Numbers 1
Figure 2
Vibrato Line Box
used with circuits shown in Figures 6, 7, 8
Figure 3
Vibrato Line Box
Used with circuit shown in Figure 9
Figure 3a
Vibrato Line Box
Used in B3, C3, RT~3 after c. 1957 and all
A-100 and D-100 organs
These pictures are to represent style design only
3
SCHEMATIC DIAGRAMS
Figures 6, 7, 8 and 9 show four different vibrato circuits which have been used in
various models. As the components of different types are generally not
interchangeable, it is important the model and serial number be furnished when
ordering replacement parts.
Non~Selective Vibrato
Figure 6, used in all consoles with -V in the model designation, has a 25 section
vibrato line. It is wired (to minimize the number of compensated pick-off points)
so that the last part of the line is used for #1 vibrato. The vibrato switch has
positions for three degrees of vibrato (VI, V2 and V3) with three off positions
between them, and there is a separate vibrato chorus switch. A resistor connected
to the off side of the chorus switch serves to maintain constant volume for the
two switch positions. The switch is not intended to be left in its middle position.
The preamplifier used with this circuit is actually two separate cascaded amplifiers
on one chassis, with the vibrato system connected between them. The first section
drives the vibrato line, and the second section amplifies the signal picked up by
the scanner. The vibrato off contact in the vibrato switch carries non-vibrato
signal directly to the second section of the preamplifier. The complete schematic
circuit of a console of this type is shown in figure 7 of Section 2, and the
preamplifier in figure 6 of Section 16, Part 2.
4
SIDE BRUSH
TENSION SPRING
ROTOR CONTACT PIN
ROTOR INSULATOR
END BRUSH MOUNTED
ON LEAF SPRING
SIDE BRUSHES
ROTOR PLATES
STATIONARY PLATES
A-BRUSH COVER REMOVED TO SHOW BRUSHES
B - VIEW WITH SCANNER COVER REMO/ED ,
(2 SETS OF PLATES REMOVED TO SHOW ROTOR)
FIG. 5 SCANNER
Selective Vibrato
Figure 7, used in early selective vibrato consoles, also has a 25 section line.
To obtain correct phasing of the vibrato and no vibrato channels, the first
part of the line is used for #1 vibrato. The vibrato switch has no off position,
and three vibrato chorus positions (Cl, C2 and C3) are included in it as well as the
three vibrato positions (VI, V2 and V3). The vibrato effect is turned on and off
each manual separately by means of vibrato swell and vibrato great tablets on the
manual assembly.
The preamplifier used with this circuit, has two separate channels into which
signals from the vibrato great and vibrato swell tablets are fed. The vibrato
signal goes through a preliminary amplifier, through the vibrato system, and then
into additional stages of amplification. The no vibrato signal also has a
preliminary amplifier, but bypasses the vibrato system and goes directly into the
additional amplifier stages. The preamplifier alone is shown in figures 20 and 20A
of Section 16, Part 2.
Line with Resistor Dividers
The vibrato line box of figure 8 employs resistors for voltage dividers at the
compensated pick-off points instead of condensers. Otherwise this circuit is
identical with that of figure 7. The line boxes of these two types are
interchangeable, and the scanners and switches are identical.
5
Coupled Line
Figure 9 shows the coupled-coil type of vibrato line box. It is smaller in size and
requires only 18 sections to give the same amount of vibrato effect as the 25
sections previously used. The switch has one less contact in each position, and so
neither the vibrato line nor the vibrato switch is interchangeable with earlier
types. The preamplifier are the same as those used with the circuits of figures 7
and 8. The scanner has somewhat different wiring harness.
OUTPUT OF
U6E0 IN ALL MODEL. AV, feV, 6CV, CV, OV, AND RT CONSOLE. &
6
MODEL. 6-2 CONSOLES SERIAL NUMBER 57305 70 45900, AND 44101 TO 44154
MODEL C-2 CONSOLES SERIAL NUMSER 38725 TO 44941
MODEL RT-2 CONSOLES SERIAL NUMSER 2051 TO 2735
FIGURE 9 -VIBRATO SYSTEM
Model B-2 Serial # 45901 - 46100, and 46155 and above
Model C-2 Serial # 46962 and above
Model RT-2 Serial # 2736 and above
Models B-3 and C-3 Serial # 56000 and above
Model RT-3 Serial # 4000 and above
Model A-IOO and D-IOO all
7
THE HAMMOND ORGAN WITH PERCUSSION
Percussion tones are available only on the upper manual (with the B adjust key
depressed) of all consoles with the suffix -3 in their model designation. These
consoles, except for the four percussion control tablets in the upper right hand
corner, look and function similar to consoles with the suffix -2 in their model
designation, when the percussion effect is not in use.
1. THEORY OF OPERATION
The percussion tones are produced by borrowing the 2nd or 3rd harmonic signal
from the corresponding drawbar (of the upper manual B adjust key drawbar group) ,
amplifying it, returning part of it to same drawbar, and conducting the balance
through push-pull control tubes, which when keyed cause the signal to fade away at a
pre-determined rate.
2. GENERAL CICUIT OPERATION (All Reference Is To Figure 24 Section 16, Part 1)
With percussion tablet on, upper manual B adjust key and an upper manual playing
key pressed, the 2nd or 3rd harmonic signal appearing on an upper manual busbar is
conducted through B adjust key drawbar wire to input of percussion amplifier
(terminal H) and amplified by T4 and V5. Besides providing push-pull signal for the
control tube V7, the percussion input transformer T5 has a third winding which feeds
the signal back to the 2nd or 3rd harmonic drawbar through equivalent key circuit
resistor R50 and terminal J. Thus the signal that was borrowed from the 2nd or 3rd
harmonic drawbar for the percussion amplifier is replaced.
When a key is depressed the signal first sounds loudly through the control tube,
transformer T6, a high pass filter, and terminal D to the grid of V4. Immediately
condenser C31 in the control tube grid circuit begins to discharge, causing the
signal to fade away. Terminal K (approximately +25 volts) is connected to the
8th harmonic B adjust key drawbar wire which is connected to manual busbar. When an
upper manual key is pressed, terminal K is grounded through the tone generator
filters. This virtually grounds the plate of V6 (connected as a diode), stops
conduction, and isolates cathode and control tube grid circuit. The grid then drifts
from approximately +25 volts to about +15 volts, at a rate determined by the time
required for C31 to discharge through R57 and R58. At the completion of this
sequence the percussion signal is blocked. No further percussion effects occur until
all keys of the upper manual are released and control grids can again rise to +25
volts. The rate of this rise is fixed by the time required to charge C31 to +25
volts through R55 and R56.
3. FOUR PERCUSSION CONTROL TABLETS, CUTOFF CONTROL, AND THEIR FUNCTIONS
The Percussion On-Off Tablet when turned on does five things to the signals of the
upper manual B adjust key drawbars.
(a) It disconnects the 2nd harmonic drawbar from its signal wire.
(b) It disconnects the 3rd harmonic drawbar from its signal wire.
(c) It connects the 2nd or 3rd harmonic drawbar signal wire (depending on position
of Harmonic Selector Tablet) to input of percussion amplifier.
(d) It disconnects the 8th harmonic drawbar from its signal wire. This wire
(connected through generator filters to ground when any key is pressed) is connected
to terminal K. The 8th harmonic signal is not available on the upper manual as long
as percussion tablet is on.
7
(e) It inserts resistor RI in series with upper manual matching transformer (T2)
secondary to reduce upper manual organ signal so that lower manual will musically
balance with the combined upper manual organ and percussion signals.
The Preset Percussion Switch is not part of the control tablet assembly or
percussion on-off tablet, but functions as an interlock with it. It is located under
the upper manual B adjust key. This switch insures that the full upper manual
signal is restored by shorting out series resistor Rl introduced by the percussion
on tablet when any other upper manual preset or adjust key is pressed. The Volume
Tablet in soft position shunts resistor R46 across the percussion output
transformer, reducing percussion signal, and also shorts out upper manual matching
transformer compensating resistor RI thus restoring upper manual signal strength to
provide proper balance between the manuals.
The Decay Tablet in fast position shunts resistor R57 across the slow decay
resistor (R58) reducing time for decay capacitor C31 to discharge and for V7 control
grids to reach cut-off. Also to preserve the same effective loudness in fast decay
position as in slow decay the control tube bias is reduced by disconnecting R59 and
allowing control tube grids to become more positive which increases output signal
about 50%.
The Harmonic Selector Tablet does three things to the signals of the upper manual
B adjust key drawbar group:
In Second Position:
(a) It connects the 2nd harmonic signal wire to percussion amplifier input.
(b) It connects the 3rd harmonic signal wire to the 3rd harmonic drawbar.
(c) It connects the signal from terminal J to 2nd harmonic drawbar.
In Third Position:
(a) It connects the 3rd harmonic signal wire to the percussion amplifier input.
(b) It connects the 2nd harmonic signal to the 2nd harmonic drawbar.
(c) It connects the signal from terminal J to 3rd harmonic drawbar.
The Percussion Cut-off Control which is located on the amplifier should be re-
adjusted as follows whenever control tube V7 is replaced:
Set expression pedal wide open, both volume tablets normal, percussion on,
percussion decay fast, and harmonic selector in either position. Depress any key in
upper half of upper manual and then adjust cut-off control exactly to the point
where signal becomes inaudible.
8
THE HAMMOND ORGAN
- 11 -
AMPLIFICATION
HAMMOND ORGAN COMPANY
North Western Avenue - Chicago
Diversey Ave - Chicago
North 25 th Avenue - Melrose Park
Copenhagen Court - Franklin Park
Illinois
USA
THE AMPLIFICATION SYSTEM
The electrical impulses which produce the tones of the Hammond Organ are
given their original amplification by a preamplifier located in the console, and are
then transmitted to the power amplifiers which are located in the tone cabinets. It
will be noted that no power transformer is included in the preamplifiers shown in
figures 1 through 9, the required plate current being supplied by the power
amplifier in the first tone cabinet. Later models of preamplifiers have a complete
power supply incorporated within them.
A tone control is included in all preamplifiers whereby the relative intensity of
the high and low frequencies may be changed to suit acoustical conditions by varying
the amplitude of the higher frequencies. On tremulant equipped consoles this control
will be found under a screw cap located toward the right end of the chassis, while
on consoles equipped with the Hammond Vibrato this tone control will be found under
the cap marked HI IMP INPUT. Selective vibrato consoles have the tone control
located midway on the preamplifier chassis.
A microphone or phonograph pickup may be used with the organ if special
circumstances make it desirable. On tremulant type consoles the input terminal,
marked P on the preamplifier, goes through a screen bypass condenser to the screen
of the input tube. This terminal is normally grounded, and the input device should
have an impedance of 500 ohms or less in order not to reduce the volume of the
organ. A signal level of a volt or more is required to drive this point, and
therefore it is suggested that the microphone or phonograph be connected through a
suitable preamplifier having an output impedance of about 200 ohms.
On vibrato consoles the input terminal, located under the cap marked HI IMP INPUT
on the preamplifier, goes to the grid of one input tube. This circuit has an input
of 1 megohm impedance and requires an input signal of about 60 millivolts maximum.
Most preamplifiers used on selective vibrato type consoles are equipped with a
standard phonograph input jack. The input impedance is approximately 1 megohm and
the circuit requires a maximum input signal of about Vi volt.
The push-pull signal line from the preamplifier output transformer to the tone
cabinets has a total impedance of approximately 200 ohms. As it is connected
directly to the grids of the power amplifier input tubes, practically any number of
power amplifiers may be connected in parallel.
The section on cables and plugs shows methods of connecting amplifiers to
the console.
When making tube replacement, output tubes in the amplifier should be checked for
similar plate current readings. If tubes have been in service for a considerable
length of time it is usually advisable to change all tubes at one time rather than
to try to match new tubes to the old ones.
1
PREAMPLIFIER ANALYSIS FOR CONSOLES PRIOR TO USE OF THE AO- 10
It is suggested that amplifiers used in the Hammond Organ be tested with a
conventional radio set analyzer with AC and DC voltage ranges up to 500 volts, and
current ranges up to 100 milliamperes. With this flexibility the instrument may also
be used as a tube tester and a line voltmeter. A resistance scale on the analyzer
meter or a separate meter with self-contained battery is useful for testing
resistors in the amplifiers. It should have a scale reading up to 3 megohms.
Typical readings for an analyzer with a 1000 Ohms per Volt meter are given below.
The voltages may vary slightly if readings are taken with a meter of different
sensitivity or with ranges in variance with those specified.
Weston Model 772 type 2 analyzer is satisfactory for all necessary tests of the
organ, and when combined with a tube checker in Weston’ s Model 775 it is a complete
portable service set adequate for the Hammond technician.
POWER AMPLIFIER
Filament
Plate
Grid
Plate
volts
volte
volts
current
56
2.5 V. AO
140 (250 V.
scale)
10 (50 V. soale)
2 ma.
2A3
- 2.5 V. AC
320
50 (50 V. scale)
35-^0 ma
5Z3;
5 V. AC
450 V. AC
■i
PREAMPLIFIER
56
2.5 V. AC
250 (250 V..
scale)
9 (50 V. scale)
4 ma.
57
2.5 V. AC
50 (250 V.
scale)
2 (50 V. scale)
0.5 ma.
Screen volts
(57 tube) - 35 (50 volt scale)
If a discrepancy of 20% or more is noticed on any of the above readings, an
investigation should be made of all parts which might affect it. Any resistor
differing by as much as 30% from its rated value should be replaced. A condenser
should be replaced if its capacity has dropped as much as 20%.
For testing both generator and amplifier condensers, a neon lamp type tester is very
satisfactory. Such a tester should be capable of checking both electrolytic and
paper condensers of capacities ranging from . 001 to 30 microfarads. In every case,
condensers must be disconnected before testing, otherwise the reading will be
affected by other parts of the circuit.
2
All resistors are marked with the standard RMA color code. The colors represent
numbers as follows:
0- black
1- brown
2- red
3- orange
4~ yellow
5~ green
6~ blue
7- violet
8- grey
9- white
The body color of the resistor is the first digit of its resistance value; the end
color is the second digit; and the dot or center band represents the number of
ciphers after the first two digits. If no dot or center band can be seen, then it is
the same as the body color. For instance, the resistance for a red body, green end
and orange dot or center band would be all follows: first digit 2, second digit 5,
followed by three ciphers: thus, 25,000 ohms.
Chokes and audio transformers may be tested by reference to their direct current
resistances given with the circuit diagrams. If a winding is broken, the resistance
will be infinite, and a short circuit will be indicated by greatly reduced
resistance. The power transformer and filament transformer may be checked by
comparing their voltages with those given on the diagrams. It should be remembered
that all given voltages are for 115 volt A. C. line and for any reduction in line
voltages they will be correspondingly affected.
3
THE HAMMOND ORGAN
- 12 -
REVERBERATION
HAMMOND ORGAN COMPANY
North Western Avenue - Chicago
Diversey Ave - Chicago
North 25 th Avenue - Melrose Park
Copenhagen Court - Franklin Park
Illinois
USA
REVERBERATION CONTROL
Reverberation control is an important feature of any Hammond Organ installation.
This device is enjoying wide acceptance because it produces reverberation in
variable degrees so the Hammond Organ, when installed in an acoustically dead
enclosure, sounds very much like an organ played in a large acoustically live
church or auditorium where organ music, enhanced by considerable reverberation
sounds at its best.
Reverberation is the prolongation of sound by repeated reflections or echoes, and is
measured by the time required for a sound to become inaudible after the source of
sound has been stopped. It is present in some degrees in all enclosures, and music
is more pleasing to the ear when accompanied by some amount of reverberation. This
is particularly true of organ music.
Reverberation results from the fact that the longer path traveled by reflected
sound causes a delay in hearing the reflected sound waves. This is easily realized
in the case of sharp staccato sounds and a fairly distant reflecting surface, as the
delayed sound is then heard separately from the direct sound and is recognized as an
echo. When music is played in a large room however, the sound echoes and re-echoes
repeatedly until absorbed by the surroundings. The Hammond reverberation control is
an electro-mechanical device which introduces multiple echoes by means of
reflections within a network of coil springs and thereby provides adequate
reverberation in locations where the natural reverberation is not sufficient.
OPERATION OF FLUID TYPE
The fluid type reverberation unit (see figure 1), about 4x5 inches in cross
section and about 4 feet high, is connected to a reverberation preamplifier built
into the power amplifier. (In some models of tone cabinets the reverberation
preamplifier is a separate unit connected to the power amplifier by cables. ) The
entire equipment is attached to the organ tone cabinet.
Reverberation is applied to the organ music after it leaves the console. Part of
the console signal goes directly to the power amplifier and part goes into the
reverberation channel, after suitable amplification.
The electrical signal fed into the reverberation unit is converted into mechanical
energy by a moving coil driver unit, similar to a dynamic speaker without a cone.
The mechanical waves are transmitted through coil springs, which have the
property of conducting sound vibrations much more slowly then the speed of sound
waves in air. In this way a spring of convenient length can introduce a delay
equivalent to that obtained in a large hall.
The driver unit, at the top of figure 2, introduces up-and-down vibrations into
the stirrup directly under it. The two enclosed springs under the stirrup hold
it in position but permit it to move freely up and down, and the spring at the far
left balances the pull of the others. These three springs are almost entirely
immersed in damping fluid, as they act largely as dampers to stabilize the response
of the driver and prevent undesired reflections.
1
UPPER LEVER
REVERBERATION UNIT
FIG. 2.
Figure 1
2
A sound wave from the stirrup travels down the open spring at the far right to the
crystal pickup, where an electrical signal is produced and conducted to the power
amplifier. This is the first reflected signal, delayed about 1/15 second from the
part of the original signal which went directly to the power amplifier.
The same wave from the stirrup also travels down the second spring from the left,
which enters the short damping tube. At the bottom of this spring the wave is
reflected back along the spring, reduced in intensity by the damping action of the
fluid. At the stirrup the horizontal lever transfers the wave to the right-hand
spring, and it goes on to the crystal to produce a second reflected signal about
3/15 second after the direct signal.
Very little of the energy of each wave is absorbed by the crystal, and the rest
is reflected back along the spring. The first reflected signal traverses the
right spring, is transferred by the lever, and goes down the spring to the short
damping tube.
Here it is reflected in reduced intensity, retraces the same path to the crystal,
and produces a third reflected signal about 5 /15 second after the direct signal.
The second reflected signal is similarly repeated, and this process continues
over and over, giving a series of signals about 2/15 second apart, until the
vibration is dissipated by fluid friction in the short tube. Just above the short
damping tube a reflecting pin attached to the spring causes partial reflection of
high frequencies and helps to make the overall response more uniform.
The damper felt avoids undesirable transverse vibration of the springs.
A greater amount of fluid in the short tube will cause increased energy loss at
each reflection and thereby reduce the number of audible reflections. Adjusting
the level of fluid in this tube, therefore, changes the reverberation time and
simulates enclosures of different sizes.
A reverberation selector switch in the amplifier circuit following the crystal can
be adjusted to pass more or less of the reflected signal in proportion to the direct
signal. While this does not actually change the reverberation time, it is a
convenient way to change the amount of reverberation instantly. Generally,
therefore, the fluid level in the short tube is left constant, at the position
recommended on the tone cabinet instruction card, and the switch is used to select
the best amount of reverberation for each installation.
The photograph of the reverberation unit (figure 1) shows a reverberation
preamplifier of the type used in kits for installation in some non-reverberation
tone cabinets. In later reverberation type tone cabinets the power amplifier is
wired so that this preamplifier is unnecessary.
Amplifier circuits associated with the reverberation unit are shown in the
section containing amplifier diagrams.
3
INSTALLATION OF FLUID TYPE
In installations of tone cabinets using type F, type G, and type H power amplifiers,
only a single reverberation unit is necessary for any installation, regardless
of the number of tone cabinets used. The reverberation unit is connected to the
first power amplifier (the one to which the console cable connects) and the
reverberated signal is supplied from that amplifier to additional cabinets.
An exception occurs in the case of type HR-40, KR-40 and JR-20 tone cabinets,
in which no reverberated signal is available for additional cabinets (because of
the separate bass and treble channels). If reverberation is desired on several
H, J, or K series cabinets, each must be equipped with a reverberation unit.
When two or more types of cabinets are used in any installation, it is preferable
that any H or K series cabinets be connected to the console ahead of any cabinets
having type F, type G. or type H amplifiers in order that reverberated signals may
not enter the bass amplifier channel. Otherwise there may be objectionable
irregularities in the response of the lower pedal notes. Further information on the
use of reverberation may be found in the section covering Acoustics.
FILLING AND ADJUSTMENT OF FLUID LEVEL
When installing a reverberation unit or tone cabinet, the damping fluid (furnished
in bottles with the unit) should be added with care, following directions on the
tone cabinet instruction card. The level in the three long tubes is not critical;
for best damping it should be near the top. but not high enough to spill if the unit
is moved. Enough fluid is furnished to fill each tube to about one inch from the
top.
The short tube should be filled to exactly 3 -1/4 inches from the top, using the
special suction bulb supplied. This amount of fluid gives the best reverberation
effect for average conditions.
If acoustic conditions are very unusual, or if an organist has a definite preference
for greater or less reverberation, the level in the short tube may be set higher or
lower. Lower fluid level will give longer reverberation time and higher fluid level
will give shorter time. There is a temperature effect due to change in viscosity of
the fluid (lower temperatures will shorten the reverberation time and higher
temperatures will lengthen it) but no adjustment for this effect is necessary unless
the temperature is consistently below 50 degrees F or above 95 degrees F.
The reverberation selector switches are set at HI when leaving the factory, and
should be readjusted on installation to give the most desirable reverberation
effect. If there is any uncertainty as to the proper adjustment, it is generally
preferable to allow too much reverberation rather than too little.
4
OPERATIONAL ADJUSTMENTS OF FLUID TYPE
It is a well known acoustical phenomenon that audibility of some frequencies is
emphasized over others in any given enclosure. Range of frequencies affected
depends upon the size and type of reflecting surfaces such as walls and ceilings.
Thus if a musical instrument such as an organ is played in an enclosure of almost
any size, some frequencies will sound louder in one portion of the listener area
than in another, and conversely some frequencies will sound weak. This can be
effectively demonstrated by playing the organ in a small room with a microphone,
then listening to the signal picked up by the microphone in another room. Variations
in loudness will be startling especially when single frequencies are sounded.
The reverberation unit similarly produces a response pattern which tends to
emphasize some frequencies over others to a slight degree. This is an operating
phenomenon of the equipment and cannot be eliminated. This room pattern effect has
not proved seriously objectionable, because as described above it stimulates an
acoustical effect which is present in some degree whenever any musical instrument
producing a wide range of frequencies is played in an enclosure.
If some notes on the organ sound excessively loud while others sound weak it may be
traceable to the reverberation control system. In investigating this, disconnect the
reverberation system by turning the switch on the reverberation preamplifier or
amplifier to the off position. 1£ notes then sound at equal loudness, turn
reverberation system on again and make the following adjustments:
1. The two-pole plug, which is connected to wire carrying signal
to the driving unit at the top of the reverberation unit, may be
inserted in two positions. Reversing this plug by turning it at 90 degrees
will reverse the input signal phase, thus changing the response
pattern of the reverberation system. Reversing this plug will
often improve evenness of overall frequency response for a
given installation.
2. Sometimes evenness of frequency response can be improved by
cutting down amplitude of the reverberated signal. This is accomplished
by changing the position of the reverberation switch.
If switch is on HI move it to Med, and if switch is on Med
move it to Lo.
Exact recommendation on adjustment of this switch is somewhat difficult as the
purpose of the reverberation control is to compensate for lack of natural
reverberation. Adjustment of it therefore should be made in cooperation with the
organist, who must understand its intent. In large installations the use of two
reverberation units will reduce room pattern to the point where it is negligible.
5
MOVING THE FLUID TYPE
The reverberation unit appears to be a delicate device but when once set up it is
very dependable and requires no further attention. When a tone cabinet is moved even
a few feet, however, the reverberation unit must be locked to avoid excessive
vibration of the springs. If the cabinet is to be tilted, the unit must be removed,
to avoid spilling the fluid, and replaced after moving. If the unit itself cannot be
kept upright while moving, the fluid must be drained and later replaced. Hammond
damping fluid is a grade especially selected for this purpose, and no other kind
should be used.
Failure to lock the unit when moving usually necessitates replacement of
the complete driver assembly or the upper or lower lever assemblies
which are a part of it. When parts are replaced, the springs must be balanced
as follows:
In a complete driver assembly ordered for replacement, the
wire passing through the unit from the upper lever to the stirrup
is not soldered. It should be left unsoldered until this adjustment
is made. Replace the driver assembly and attach all the
springs; check and adjust the single damping tube, if necessary,
to make the upper lever assembly level. Then solder the wire
to the small tube passing through the voice coil. When only the
upper or lower lever assembly is replaced, the wire need not
be unsoldered, but the upper level must be made level by adjusting
the single tube.
6
OPERATION OF DRY TYPE
A later reverberation device. Figure 3. is an improved unit which employs a dry
damping means instead of the liquid previously used. It has improved
driver and pickup elements and has three transmission springs instead of the
one formerly used.
The device is about fourteen inches high, thirteen inches wide and two inches in
depth. It is incorporated in the new PR-20. PR-40 and QR-40 tone cabinets.
In operation, an electrical signal from an amplifier is applied to the driver
unit in the reverberation device which then converts the electrical signal into
mechanical energy which is fed into the three springs of different lengths. The
signal takes 1/22 second to traverse the shortest spring to the pickup, which
reconverts part of the energy to an electrical signal and reflects most of the
energy back along the spring to the driver, where again most of the signal is
reflected back along the spring to the pickup. This transaction continues until the
signal energy at the pickup is reduced to one millionth of its original value. This
period is about two seconds in duration. The other two springs operate in a similar
fashion, but their reflections occur at longer time intervals, 1/17 and 1/15 second
respectively. The amount of damping for each of the three springs is so proportioned
that they have a uniform decay rate.
OPERATION IN PR AND QR SERIES TONE CABINETS
The dry type reverberation device mounted in the PR and OR series tone cabinet
functions as follows. Part of the console signal is applied to the reverberation
driver and the resultant reverberated signal at the pickup is separated into two
frequency bands, one occupying the spectrum from thirty-two to two hundred cycles,
and the other from two hundred cycles to six thousand cycles. The low frequency
reverberated signals are mixed with the direct console signals, amplified and fed to
the low frequency speakers. The high frequency or treble reverberated signals are
amplified and fed to a separate speaker system, while the treble signals from the
console are also amplified and fed into another speaker system. In other words, the
low frequency direct and reverberated signals are electrically mixed and the
high frequency direct and reverberated signals are acoustically mixed.
Two selector switches are mounted on the side of the PR and OR series tone cabinets
to provide a variation in the amount of reverberation produced. The bass
reverberation switch provides increased direct output as the amount of reverberated
signal is reduced. This is accomplished by introducing more or less direct signal
into the bass channel as the amount of reverberation is decreased or increased. The
treble reverberation switch controls the gain of the treble reverberation amplifier
channel, but if the switch is turned to the Reverberation Off position, the direct
console treble signal is fed into this channel to provide full treble acoustic
output from the cabinets.
7
INSTALLATION OF PR AND QR TONE CABINETS
When these tone cabinets are installed the Room Size control on the rear of the
amplifier chassis should be adjusted in accordance with the instruction card in the
tone cabinet, and the reverberation device should be unlocked. Warning : Whenever
the cabinet is moved, even one or two feet, the reverberation device should be
locked. Failure to do this may cause one or more springs to become unhooked from the
driver or pickup assembly.
Tone cabinets embodying this reverberation unit do not provide a reverberated signal
to other tone cabinets. If more than one tone cabinet of the type normally embodying
this unit is used and reverberation is desired from all tone cabinets, then a
reverberation unit must be included in each tone cabinet.
Kits are available which will permit turning the reverberation on and off from the
console without the use of additional cables. Several different kits are available,
depending upon the type of console , and the instruction sheet accompanying each kit
describes the installation and operation. These kits are designed for use with PR
and QR series cabinets only.
SERVICE SUGGESTIONS
Should no reverberation be evident in playing a tone cabinet equipped with this
device, but a loud noise results from touching the springs, it is quite likely that
the locking device has not been completely opened. Make sure that the springs of the
unit are free of the clamps, which are located near the driver and pickup.
If in moving a tone cabinet a spring is disengaged from the driver or pickup,
the ends can again be reinserted in the loops. For proper operation it is suggested
that the reverberation unit be removed for this operation and the loose springs be
allowed to hang quietly, then the end should be picked up and inserted in the loop
from which it became disengaged. The purpose of this procedure is to eliminate any
twist within the spring which could cause erratic noises in operation because of
torque which would be transferred to the pickup portion.
9
THE HAMMOND ORGAN
-13-
PEDAL SOLO UNIT
HAMMOND ORGAN COMPANY
North Western Avenue - Chicago
Diversey Ave - Chicago
North 25 th Avenue - Melrose Park
Copenhagen Court - Franklin Park
Illinois
USA
CONCERT MODEL CONSOLES
(Pedal Solo schematics referenced here
will be found in the Wiring Diagrams and Schematics section.
Block diagrams can be found in General Descriptions)
The Model RT Hammond Organ console is similar electrically to the Model CV console,
but differs in the following respects:
1. The console woodwork is larger and somewhat different in depth.
2. The pedal keyboard is concave, with 32 pedal keys.
3. The pedal solo unit is added to provide deep and rich pedal tones
desired by the concert organist.
The Model RT-2 console includes the above feature and also has the selective vibrato
system as used in Model C~2.
The Model RT-3 console is similar to Model RT-2 with the addition of the percussion
feature.
The Model D-100 console is similar to Model RT -3 with the addition of a built in
power amplifier and speakers.
PEDAL SOLO UNIT
The pedal solo unit incorporated in these consoles provides a series of bright pedal
solo tones in addition to the usual pedal accompaniment tones available on other
models. The pedal solo tones, generated by a vacuum tube oscillator circuit, are
controlled by a volume control knob and eight tilting stop tablets, of which one
turns all the pedal solo tones on or off and the others provide various pitch
registers and tone colors. The pedal solo unit is independent of the electromagnetic
tone wheel generator and can be turned off without affecting the remainder of the
organ.
Only one pedal solo note will play at a time (if two pedals are depressed at a time,
only the higher one plays) but this does not affect the foundation or accompaniment
tone controlled by the two pedal drawbars. It is possible therefore, for the left
foot to play a bass accompaniment note set up on the pedal drawbars, while at the
same time the right foot plays a pedal solo note (the accompaniment tone on this
higher note being masked by the high solo quality).
The pedal solo unit is designed as a part of these consoles, and because of
mechanical limitations it is not adaptable to any other model.
NOTE: Pedal solo generators of all types have slightly different electrical circuits
but are interchangeable in all RT & D-100 series consoles. Type RTA was used in
all Model RT and some Model RT-2 consoles. Types RTB and RTC were originally
used only in Model RT-2. Types RTD and RTE have improved components - but no change
in circuits.
1
HOW THE PEDAL SOLO UNIT WORKS
All notes of the pedal solo unit are controlled by a two-triode vacuum tube master
oscillator circuit operating at audio frequencies from 523 to 3136 cycles per
second, corresponding to 1 foot pitch. Thus the master oscillator operates over the
full pedal keyboard range of 32 notes. Each time a pedal is depressed, its tuning
contact tunes the oscillator to the pitch associated with the corresponding key in
this 32 note range.
The output of the oscillator is fed into a series of five cascaded frequency
dividers, each of which divides its input frequency by two and thus produces a note
an octave lower than its input frequency. The five dividers thereby provide pitches
of one, two, three, four, and five octaves below the pitch of the oscillator. In
this way, when the oscillator is tuned to some given note, each divider produces a
note in exact octave relation to the oscillator, thus forming a series of six notes
having exact octave relationships. The particular frequency divider or dividers
selected for sounding through the amplifier and speaker system of the organ will
depend upon which of the stop tablets are used.
A control contact Under each pedal causes the control tube to transmit the signal to
the amplification system with a controlled rate of attack.
COMPONENTS OF THE PEDAL SOLO UNIT
Electrically the pedal solo unit is very similar in principle to the Hammond Solovox
Model L, although there are, of course, many differences. It employs tuning coils,
tuning adjustment knobs, a master oscillator, and frequency dividers similar to
those in the Solovox, and the stop tablets are similar in function to the register
controls of the Solovox.
The Pedal Solo Generator is a chassis which looks like an amplifier and contains the
master oscillator, five frequency dividers, an amplifier, a control tube, and a
power supply. It is located directly above the pedal switch assembly, near the left
side of the console as viewed at the rear.
The Tuning Coil Assembly contains 32 adjustable inductance coils, which tune the
master oscillator to the frequencies of the 32 pedal notes. It is mounted above the
pedal switch assembly, near the right side of the console as viewed at the rear.
The Control Panel , with stop tablets and a volume control knob, is mounted at the
right end lower manual.
The Pedal Switch has nine contacts under each pedal key. One is used for tuning the
pedal solo unit, the second serves to key the amplifier and make the pedal solo note
sound, and the other seven carry harmonics from the main (tone wheel) generator to
the pedal drawbars as in the B and C series consoles.
2
WIRING DIAGRAMS
In studying the operation of the pedal solo unit, refer first to the block diagram
(figure 1) and second to the more detailed schematic circuit (figure 2, 2B or 2C) .
The schematic diagram of the console, apart from the pedal solo unit, is the same as
for the Model CV, 02, or 03 console, shown in Section 2. Actual connections
between the pedal solo unit and other parts of the console are shown in the section
containing the console wiring diagrams.
The Oscillator
The 32 coils which tune the audio frequency oscillator are shown in figure 2. When
the lowest C note is played (this pedal has no tuning contact), all 32 coils are
connected in series to form the tuning inductance of the oscillator. When any other
pedal is depressed, its tuning contact shorts out some of these coils (making less
total inductance) and thus tunes the oscillator to the higher pitch associated with
that note. If two pedals are depressed at the same time only the higher pitched of
the two will sound.
Frequency Dividers
Each divider includes three triodes. One acts as a driver and pulse rectifier,
supplying sharp and narrow negative pulses to actuate a symmetrical feed-back
tripping circuit comprising two triodes. Either one (but only one) of these two
triodes can be conducting at a time, for by drawing plate current it holds the other
in a cut-off condition.
Suppose, for example, that the first triode is conducting and the second is cut off.
Now a negative input pulse impressed on the grids of both triodes will not affect
the second one, which is already cut off, but will cut off the first. This produces
a positive pulse at the plate of the first triode, which is applied to the grid of
the second triode through its feedback connection. The second triode then suddenly
conducts current, producing a negative pulse at its plate. This negative pulse,
applied to the first triode grid through its feed-back connection, insures that the
first triode remains cut off. The situation is now exactly reversed, with the first
triode cut off and the second conducting.
The next input pulse will act on the second triode, cutting it off again and making
the first conductive; and thus two input cycles are required to produce one output
cycle. Each frequency divider circuit therefore divides its input frequency in half,
producing an output signal one octave lower than the preceding divider. One triode
plate of each divider stage furnishes a signal of rectangular wave shape to the
following driver tube, and output signals are taken from the driver and divider
plates as indicated in figures 2, 2-B and 2C.
This divider circuit is capable of operating satisfactorily with wide variations in
voltage, input frequency, and values of components, and therefore is remarkably
stable and requires no adjustments.
3
Stop Tablets
From the preceding, we see that whenever any one of the three G pedals, for
instance, is depressed, the frequency dividers, together with the oscillator,
provide a series of six G notes in exact octave relations. The particular divider
whose output is to sound is selected by the stop tablets: 2’ & 1’ , 4’ , 8’, 16’ , 32’
BOMBARDE and 32’ BOURDON. Thus the stop tablets act as register controls to shift
the pitch range of the pedal solo unit to five different positions. If two or more
of these controls are turned on simultaneously, a composite tone will be heard,
consisting of the output of several dividers simultaneously sounding in their octave
relations. (A tablet is on when the white dot is visible. )
Note With Regard To The 32-foot Stops
In playing, care must be exercised by the organist in using the 32’ BOURDON and 32’
BOMBARDE pedal stops. They are useful in permitting the player to obtain deep
bass notes in the second octave of pedals. As the player descends into the first
octave of pedals, he will find that the B, A#, A, and G# pedals have a definite
pitch like the higher pedals. However, below the G# pedal, it becomes difficult to
ascribe a definite pitch to these 32-foot tones. When a 32-foot stop is registered
in concert organ music, it will be found that the pedals required will rarely be
lower than the G pedal in the first octave. Therefore, do not use the 32-foot pedal
stops indiscriminately, for ordinary bass purposes where the 16-foot tone is
desired. The 32’ BOURDON stop produces an effect which is mostly felt as a very low
bass undulation when playing low in the first octave of pedals. The 32’ BOMBARDE is
always used in conjunction with other higher pitched stops. When played by itself in
the lower half of the lowest octave of pedals, the effect is of such low pitch as to
be of little use musically.
MUTE
Pressing the mute tablet shunts a small condenser across the signal circuit to
reduce the intensity of the higher frequencies. This is effective on all the pedal
solo stops to make the tones more mellow.
PEDAL SOLO ON
This tablet, connected in series with the keying contacts in the pedal switch, turns
on and off any solo combination set up on the other tablets. It may thus be used as
a preset control for the pedal solo unit.
Volume Control
The volume knob on the control panel is used to balance the pedal solo tones with
the rest of the organ. The overall volume of the entire organ, including the pedal
solo unit, is controlled by the expression pedal.
Control Tube
The push-pull control tube, a double triode, is normally cut off by a large negative
bias applied to its grid circuit. When any pedal is pressed its control contact
grounds this bias circuit (if the PEDAL SOLO ON tablet is on) , thereby removing the
bias and causing the note to sound. A condenser and resistor, C81 and R112, make the
tonal attack smooth. The control tube is connected to an output transformer whose
secondary feeds the pedal solo signal through the volume control to the organ preset
panel, where it is combined with the other tones of the organ.
4
Tuning
All notes of the pedal solo unit are simultaneously tuned by adjusting two tuning
knobs located on the pedal solo generator. These change the frequency of the master
oscillator by shunting small additional capacitors across the main tuning condenser.
To tune the pedal solo unit to the organ, proceed as follows:
(a) Press only the 4, MUTE, and PEDAL SOLO ON tablets and hold down the middle D#
pedal. The pedal drawbars must be pushed in, and the vibrato should be off.
(b) Pull out only the first white drawbar for either manual and press the
corresponding preset key. Hold down the D# key above the middle C, with the
drawbar and the volume control knob set to give approximately equal volume.
(c) Set the fine tuning knob on the pedal solo generator to its center position
and adjust the rough tuning knob to the point which brings the two notes most
nearly in tune (slowest beat between them). Then adjust the fine tuning knob
to make the beat as slow as possible. While it is generally not possible to
tune exactly to zero beat, the accuracy of tuning provided will be found to be
sufficient.
(d) The organist may prefer to have the pedal solo generator tuned slightly sharp
to increase the chorus effect between it and the main tone generator. To tune
it sharp, turn the fine tuning switch counterclockwise one step.
Note: Never tune on the lower pitch registers (especially the 32-foot range) where
the pitch acuity of the ear is insufficient for accurate tuning. If the 4-foot stop
is tuned as directed above, all other registers will be in tune because they are
locked by the frequency dividers to exact octave intervals.
Wiring of Pedal Switch
The nine contacts of each pedal key make contact with nine busbars extending the
length of the pedal switch assembly. One set of contacts and the corresponding
busbar, used for tuning the pedal solo unit, are wired to a terminal panel on top of
the pedal switch, where the tuning coil cable connects. The other eight sets of
contacts are wired to the main tone generator as indicated in the pedal wiring chart
in the section on manuals and pedals, although only seven sets are actually used to
carry tones from the main generator to the pedal drawbars.
The contacts of one set (the one marked 12th harmonic in the wiring chart) are used
as control contacts for keying the pedal solo unit. The fact that they are connected
to ground through the pedal switch wiring and the tone generator wiring does not
affect their use for this purpose, since the keying circuit impedance is high by
comparison. The busbar for these contacts is wired to a terminal on top of the pedal
switch to which the white keying wire from the pedal solo control panel connects.
These contacts are wired to the main tone generator in the usual way in order that
they may supply the 12th harmonic in case special circumstances make it desirable
to omit the pedal solo unit. In this case a green wire from the pedal resistor panel
on the manual assembly (it will be found wrapped around the pedal switch cable, is
connected to the busbar terminal on top of the pedal switch (see appropriate figure
in the section of wiring diagrams). The pedal tones will then be identical to those
on the B and C series organs.
5
TUBE SOCKET VOLTAGES
For Pedal Generator Stamped “Type RTA*
For voltages of other models see corresponding schematic diagrams.
These readings are taken with a 1000-ohms -per- volt meter having three scales of
50, 250 and 1000 volts. All voltages are taken with 117 volt line, and deviations of as
much as 20 per cent may be caused by line voltage variations. The “PEDAL SOLO
ON* tablet must be “on”, and other tablets may be either on or off. No pedal should
be depressed unless specified. The negative lead of the voltmeter is connected to
ground except as noted. See figure 5 for terminal locations.
Connect Positive Meter should read Meter
Voltmeter lead to: (volts) Scale This shows voltage of:
“+290”
290
1000
1st Filter Capacitor
“■*•270”
270
1000
2nd Filter Capacitor
“♦120”
120
250
3rd Filter Capacitor
“♦ 20”
20
50
Divider Bias
Ground (neg. to “-37”)
37
50
Control Tube Bias Supply
Tube VI (term. #3)
190
1000
Master Oscillator Plate
Tube VI (term. #8)
8.5
50
(1st section)
Master Oscillator Cathode
Tube V2 (term. #2)
230
1000
(1st section)
Master Oscillator Plate
Tube V2 (term. #3)
3.5
50
(2nd section)
Master Oscillator Cathode
Tube V2 (term. #5)
180
1000
(2nd section)
Oscillator Rectifier Plate
Tube V2 (term. #6)
2
50
Oscillator Rectifier Cathode
Tube V3 (term. #2)
75
250
Driver Plate
Tube V3 (term. #5), V6 (term.
#3), V8 (term. #2 & #5)
95
250
Driver Plates
Tube V4, V5, V7, V9, V10
(term. #2 and #5)
55 to 75
250
Divider Plates
Tube V12 (term. #3)
120
250
Preamplifier Plate
Tube V12 (term. #8)
4
50
Preamplifier Cathode
Tube V13 (term. #2 and #5)
120
250
Control Tube Plates
6
Connect Positive
voltmeter Lead to:
Meter Should
Read fvolts)
Meter
Scale
This shows
Voltaee of:
Same, any pedal pressed
105
250
Control Tube Plates
Tube V13 (term. #3)
0
50
Control Tube Cathode
Same, any pedal pressed
3
50
Control Tube Cathode
Tube Vll (term. #8)
290
1000
Rectifier Cathode
AC VOLTAGES
Heater voltage to all tubes except VI 1 6 V. RMS
Rectifier tube VI 1 heater voltage 5 V. RMS
Vll term. #4 or #6 to “-37* 280 V. RMS
AC ripple across 1200 ohm resistors R99, R100, R101
(connect a 1/4 mfd. condenser in series with meter) Less than 2 V. RMS
AC ripple across 5000 ohm resistor R105 (connect a
1/4 mfd. condenser in series with meter) Less than 1 V. RMS
PRACTICAL SERVICE SUGGESTIONS
The following suggestions cover possible troubles in the pedal solo unit only.
Suggestions for the standard organ system will be found elsewhere in the service
manual.
Any trouble in the organ ahead of the matching transformer will not affect the pedal
solo unit, but trouble following the transformer will affect both systems equally.
Pedal Solo Unit Does Not Play First make sure that the tubes are lighted, all
controls are in playing position, and the rest of the organ plays normally. Several
possible causes of trouble are listed below in order of probability.
(a) Tubes. The tubes are of standard radio types and can be tested in the usual
way. Figure 3 shows their locations in the pedal solo generator
(b) Loose cable connector. See that the 15 pole plug and the shielded plug are
inserted tightly into the pedal solo generator.
(c) Keying circuit. A dirty contact in the PEDAL SOLO ON tablet or a defective
connection in any part of the keying circuit will prevent removal of the
cutoff bias when a key is played. If this is the trouble, grounding pin 15 of
the cable plug will make a pedal note sound. The following section, Procedure
for Removing Parts, tells how to reach and clean the tablet contacts.
(d) Amplifier or oscillator circuit. The amplifier circuit is conventional in
most respects, and voltage measurements will generally serve to identify any
trouble. Failure of the master oscillator will make the pedal solo unit fail
to play, and voltage readings will be helpful in this case also. Figures 4,
4A, 48 show the locations of all components, and a chart at the end of this
section gives their characteristics.
7
MASTER OSCILLATOR
AND OSCILLATOR
1ST AND 2ND 1ST 2ND
DIVIDER FREQUENCY FREQUENCY
DIVIDER
DIVIDER
DRIVERS DIVIDER
DRIVER
FRONT VIEW OF CHASSIS
o
LINE CORD
BLACK GREEN
ROUGH
TUNING
FINE
TUNING
O O
O
O
1
SHIELDF D TUNING CABLE
RECEPTACLE CONNECTIONS
CABLE
RECEPTACLE
Reference symbols for components refer to pedal solo
UNIT SCHEMATIC
TUBE TYPES IN PARENTHESES ARE USED IN TYPE RTC, RTD, RTE.
FIGURE 3-PEDAL SOLO GENERATOR
Pedal solo note does not sound on one pedal (with any combination of control
tablets). The control contact of that pedal is probably dirty and can be cleared by
adjusting the pedal busbar shifter as described in the section on manuals and
pedals. The same trouble may appear as an irregular sputtering or crackling of a
single pedal note.
This effect may also result from an open circuit in the pedal wiring, the pedal to
main generator cable, or the main generator wiring, since the control circuit is
completed through the main generator.
All pedals fail to play on one stop tablet. If all other tablets play correctly, the
signal from the oscillator or one frequency divider is not reaching the amplifier.
This may be due to a loose cable plug, a broken wire, or a dirty contact on the
tablet. In the latter case, refer to the following section, Procedure for Removing
Parts. The schematic diagram, figure 2, indicates which cable wire and frequency
divider correspond to each tablet. Figure 5 identifies the tablets and electrical
components in the control panel.
All pedals play the wrong pitch (or do not play at all) on one or more low pitched
stop tablets. One frequency divider is not operating correctly, in which case all
dividers below it will also fall. A cathode-ray oscilloscope connected from ground
to the plate of any divider tube should show a rectangular wave, while the plate
of any divider driver tube should show a very sharp and narrow negative pulse. If
electrolytic capacitor C78 ss open or very low in capacity, all the dividers may
fail to operate.
Key thumps or clicks: If capacitor C81 is open, there will be a loud thump each
time a pedal is played.
Hum: An excessive 120 cycle hum in the output will result from failure of one of the
filter capacitors C75, C71, and C78.
Tuning of individual notes: The individual note tuning system consists of 32 small
inductance coils, each of which is adjustable by moving the coll on its iron core.
This tuning system is very stable because it has practically no aging effect and is
very insensitive to ordinary humidity and temperature changes. However, after long
use under adverse climatic conditions it is possible that some pedal solo notes may
not be exactly in tune with each other.
Always tune first with the tuning knobs as indicated above. Keep In mind the fact
that it is generally desirable to have the pedal solo unit slightly out-of-tune with
the organ. If you are sure some notes actually require tuning, proceed as follows:
(a) Disconnect the two cable leads from the G~G terminals on the preamplifier and
ground the two wires. Connect one set of oscilloscope plates (either horizontal
or vertical) to one G terminal and ground.
(b) Connect the other set of oscilloscope plates to ground and to pin 3 of V6
through a blocking condenser.
(c) Remove the cover of the tuning coil box at the rear of the console, exposing the
numbered tuning coils. The wiring diagram shows the location of these coils. Set the
fine and rough tuning knobs to their center positions.
(d) Push in the pedal drawbars, turn the vibrato off, and turn all pedal solo
tablets off. Using only the first white drawbar on either manual, hold down the
second key G key from the top. Hold down the highest pedal.
(e) Loosen the clamping screw on coil 32 and slide the coil carefully forward or
backward until the note is in tune as indicated by the oscilloscope wave pattern
standing still or moving no more than one cycle in two seconds. Tighten the clamping
screw.
(f) Release key and pedal and press adjacent F# key and pedal. Adjust coil 31 in
same way. Repeat for all other pedals and coils in chromatic order downward.
It is important to start with the highest pedal and progress downward one pedal at
a time because the tuning of the lower notes is dependent upon all of the higher
coils. Each pedal adds an increment of inductance in series with all coils above
it, and adjusting any single note will detune all those below it.
9
Note: From the prior instructions you can see that tuning the individual notes is a
long and tedious process and must be done with extreme care. It should not be
undertaken unless you are absolutely certain that the tuning error is great enough
to interfere seriously with playing the organ.
PROCEDURE FOR REMOVING PARTS
To remove Control Panel and Clean Contacts
1. Remove four screws holding music rack and place it on top of console.
2. Remove two belt head manual bolts exposed when music rack is removed.
3. Remove two large hex head manual bolts located on underside of generator shelf
near rear.
4. Remove two screws passing up through right hand chassis block of lower
manual into control panel.
5. Remove one screw holding angle bracket to bottom cover of control panel.
6. Tilt upper manual upward and slide control panel assembly through opening,
toward back of console.
7. Remove bottom cover of control panel.
8. Remove four wood screws holding wood frame work to chassis of control panel.
9. Remove knob and loosen nut which holds volume control.
10. Tip wood frame up and slide back until rear wooden strip clears tablet
identification strip.
11. Slide pivot rod out of tablet assembly and remove tablets.
12. Remove four #3 screws holding tablet assembly to chassis of control panel and
tilt assembly up. Contacts are now visible and can be cleaned by wiping gently
with a cloth.
10
ELECTRICAL PARTS LIST FOR PEDAL SOLO GENERATOR
CONDENSERS
REFERENCE SYMBOL
CAPACITY
VOLTAGE TYPE
C75
20 mfd.
400
>
Electrolytic
C76
20 mfd.
300
C77
80 mfd.
150
Electrolytic
C78
30 mfd.
50
Used in Generator
C79
30 mfd.
15 ,
| “Type RTA” only
C76
40 mfd.
400 '
Electrolytic
AO-19131-1
C77
20 mfd.
350
> Not Used in Generator
C78
20 mfd.
350
‘Type RTA
C79
6 mfd.
200 j
WIRE WOUND
RESISTORS
REFERENCE SYMBOL
OHMS
WATTS
PART NUMBER
R 1051 Used in Generator
(5000
10
R 106] “Type RTA* only
(4500
5
626-060741
VARIABLE RESISTOR
REFERENCE SYMBOL
OHMS
R 118
250
TRANSFORMERS
REFERENCE SYMBOL
FUNCTION
PART NUMBER
T 1
Power 115V. 60 cy.
T 1
Power 115V. 50/60 cy.
T 1
Power 230V. 50/60 cy.
003-021320-003
T 2
Audio
T 3
Output
11
THE HAMMOND ORGAN
-14-
ECHO ORGAN EQUIPMENT
HAMMOND ORGAN COMPANY
North Western Avenue - Chicago
Diversey Ave - Chicago
North 25 th Avenue - Melrose Park
Copenhagen Court - Franklin Park
Illinois
USA
ECHO ORGAN EQUIPMENT FOR THE HAMMOND ORGAN
An echo tone cabinet (or group of cabinets) may be used with any type of Hammond
Organ console. The echo cabinet is usually placed at some distance from the console
and from the main cabinet; for instance, at the opposite end of a church. An echo
switch mounted on the console enables the organist to play through the main cabinet
alone, the echo cabinet alone, or both together. Any standard Hammond tone cabinet
may be used.
The echo switch has three positions. When it is set to the left the main tone
cabinet (or cabinets) will sound, and when set to the right the echo cabinet will
sound. With the switch in the center both main and echo will sound simultaneously.
The switch controls only the signal circuits, and all cabinets remain energized as
long as the console is turned on.
Figures 1 and 2 show how the main and echo tone cabinets are connected to the
console, and figure 3 is a schematic circuit of the echo system.
ECHO ORGAN KIT
The echo kit includes all necessary parts for installation in consoles Models B, BC,
BCV, BV, C, CV, D, DV, G, RT, B-2, C~2, RT-2, B-3, C~3, & RT-3, with the exception
of some early B and BC consoles having no outlet box. For installing kit in a
console without an outlet box, or in Model A or Model E console, see special
instructions at the end of this section.
A 5-conductor cable must be ordered separately, of suitable length to reach from the
console to the echo cabinet, in addition to the desired echo cabinet (or cabinets).
AC. ulNE CORD A C. POWER TO CABINETS IS NOT
SWiTCH SENDS SIGNAL
TO EITHER CAB'.NET
OB TO BOTH
FIGURE I. BLOCK DIAGRAM OF "ECHO" ORGAN
1
CONSOLE WITH
ECHO SWITCH
1
j A.C. LINE
5 OR 6-
"MAIN" TONE
CA9INE *
i J
ECHO" TONE.
CABINET
1
CONDUCTOR
CABLE
5-
CORD
ij
/ J
V
CONDUCTOR
T
1 cable
2-POl.
E A.C.
5-POLE
PLUG
IN
"echo cabinet"
CONSOLE
RECEPTACLE
IN CONSOLE
ADDITIONAL T OLE
CAE'NE T £, iF AN T,
VAl 3E CONNECTED
as shown n
c ‘GURlS 3,4, 5, 6,. 7
SECTION 4
5 OR 6-POLE
"MAIN CABINET*
RECEPTACLE
IN CONSOLE
FIGURE 2. CONNECTIONS OF CONSOLE
TO MAIN AND ECHO TONE CABINETS
INSTRUCTIONS FOR INSTALLING KIT
1. Disconnect chorus drawbar (if console has chorus generator) from lever inside
console by removing coupling pin. Detach vibrato chorus switch (if any) by removing
knurled nut from front. Remove four screws in music rack end blocks and remove
entire music rack assembly from console.
2. Drill holes for echo switch in music rack base as shown in figure 4. Replace
music rack and other parts. Mount echo switch.
Note : Steps 3 and 4 apply only to console models having B in the type
designation.
3. Disconnect and remove swell pedal connecting rod. If console has chorus
generator, it will be necessary to unfasten preamplifier and rheostat box
(leaving wires connected) and remove mounting channel.
4. Remove 4 screws from pedal switch cover panel, remove key at top of wiring tube
nearest to swell pedal, raise tube a few inches, and lift pedal switch cover panel.
Note : Step 5 applies only to console models having C, D, G, or R in the
type designation.
5. Remove key at top of wiring tube and raise tube a few inches to
permit detaching the outlet box.
6. Unfasten outlet box from base of console, open it, knock out proper receptacle
hole blank (see figure 5) and mount echo receptacle. Solder connections as indicated
in figure 5. Pull twisted pair of wires up through wiring tube. Reassemble outlet
box and attach it to console. Replace pedal switch cover if it was raised in step 4.
Note : For consoles not equipped with outlet box, see special instructions
at end of this section.
2
7. Replace any other parts previously removed. Fasten echo wiring panel on top of
line panel cover and connect all wires as shown in figure 5.
8. Check for proper operation. If it should happen that the echo cabinet
sounds with the switch in main position and the main cabinet sounds with the switch
in echo position, interchange the main and echo cable wires at the echo wiring
panel.
INSTALLING KIT IN CONCERT MODEL E CONSOLES
In this model the preamplifier is located so far from the line panel that the blue,
green, and black wires from the echo panel must be extended to reach the
preamplifier. In addition, the black and red cable wires must be extended to reach
the echo panel. Otherwise the installation may be made as described above.
MAIN
ECHO & ECHO MAIN
TO PREAMPLIFIER
FIGURE 3 - SCHEMATIC DIAGRAM OF ECHO KIT WIRING
3
FIGURE 4-HOLES TO BE PROVIDED FOR MOUNTING
ECHO bWITCH
*Note: On consoles with Start and Run switches in wood end block (B— 3, C-3, RT— 3) increase this
dimension to 3 & 17/32
INSTALLING KIT IN EARLY MODEL BAND BC CONSOLES WITH NO OUTLET BOX
When installing an echo kit in one of these consoles, it is preferable that an
outlet box be installed at the same time.
(a) Obtain one outlet box with 6-conductor receptacle, 2 conductor plug and mounting
screws; one 6-conductor plug, and one plug cap, stating the model and serial number
of the console.
(b) Follow steps 1, 2, 3, and 4 above.
(c) Mount echo receptacle in outlet box (see figure 5). Cut off 6-conductor cable to
proper length to connect it to outlet box, and mount 6-conductor plug and plug cap
on remaining piece of cable. Figure 6 shows connections to plug and receptacle.
(d) Follow remaining part of step 6 and follow steps 7 and 8. Figure 7 shows
position in which outlet box should be mounted on console.
INSTALLING KIT IN MODEL A CONSOLES
In this model the installation of the echo switch is complicated by the fact that
the right hand wooden end block is very thick and has no flat front surface to
accommodate the switch plate. Electrically the installation is the same as for the
other models.
4
flfx I- ECHO SWITCH MOUNTED IN
•\\ .MUSIC RACK BASE
AS SHOWN (DO NOT CHANCE
MAIN CABINET RECEPTACLE,
FIGURE 5 - WIRING OF ECHO KIT
BLACKOR BLACK
TRACER (SIGNAL)
GROUND
GREY
INDIC A TOR
RED OR RED
rRACER(SIGNAL)
BROW N
B+ (SHIELDED)
BLUE
A.C. POWER
RED OR RED
tracer (Signal^
BRCWN _ J
B+(5i-i;ELDEDj
BLACK 'jR_3L.ACK_
T R a’c er\ signal) “
Shi eld
" (GROUND)
FIGURE 6-CONNECTIONS OF CABLE TO 6-POLE PLUG AND RECEPTACLE
LEG STRETCHER AT
RIGHT END OF CONSOLE
LINE CORD ECHO CABINET
PLUG RECEPTACLE
FIGURE 7 - MOUNTING OF OUTLET BOX
ON MODEL B OR BC CONSOLE
5
MONAURAL EARPHONE CONNECTIONS
Earphones can be added to the console for practice purposes so as not to disturb
others. Earphones at best cannot replace the tonal quality achieved from the
instruments’ own speakers but do make the organ more available. One method of
attaching earphones is shown in the sketch below, using a reluctance type headset of
good quality. Inserting the phone plugs silences the speakers in the console. Wiring
is between the preamplifier terminals marked G and the main amplifier input.
STEREO EARPHONE CONNECTIONS
A second method of attaching earphones is given below. This will provide a
stereo effect that is well worth the cost and effort expended.
1. Turn over AO-39 chassis and disconnect two black wires from the BN-BK speaker
terminal inside of the amplifier. Leave output transformer lead connected. Connect
the two wires removed, to the center lug of the three lug terminal strip nearest the
front of the chassis and solder connections.
2. Replace amplifier and place a solder lug under the mounting screw nearest the
output transformer.
3. Remove the brown wire from the BN-BK speaker terminal on the AO-39 and solder it
to the lug just installed.
4. Remove the green wire from the GN speaker terminal on the AO-39 amplifier and
splice on an additional length of wire long enough to reach the earphone jack and
switch which will be mounted on the front of the console.
5. Solder a wire to the GN speaker terminal on the AO-39 long enough to reach the
earphone jack.
6. Solder a wire to the BN-BK speaker terminal on the AO-39 long enough to reach the
earphone jack.
6
7. Identify the green and black wires on the center speaker that connect to the
A0~35 or AO-44 amplifier. Remove these wires and connect the green wire to the GN
speaker terminal and the black wire to the BN -BK speaker terminal on the AO-39
amplifier.
8. Identify the speaker terminals on the reverberation amplifier AO-35 or AO-44.
If a black wire is soldered to the left speaker terminal on the amplifier, reverse
the speaker leads at the amplifier so that the gray wire is on the left lug and the
black wire is on the right lug of the amplifier speaker terminals.
9. Remove the blue wire that is connected to the speaker directly above the
reverberation amplifier. Splice on an additional length of wire long enough to reach
the earphone jack.
10. Solder a wire to the empty lug on the speaker long enough to reach the earphone
jack.
11. Solder a wire to the right speaker terminal long enough to reach the earphone
jack. (This terminal is grounded inside the AO-35 or AO-44 chassis. )
12. Mount all components to the right of the dotted line shown on the diagram
in a suitable box and connect as shown. Numbers shown under wires identify these
leads based on the preceding steps.
13. Mount box containing switch and earphone jack at a convenient point at the
front of the console.
Ipaabr
PHONO INPUT
A microphone or record player pickup may be used through the organ if desired.
The preamplifier is equipped with a standard phonograph input jack. The input
impedance is approximately 1 megohm and the circuit requires a maximum input
signal of about h volt. A volume control will have to be installed between the
microphone or record player input and the organ inasmuch as the swell control of the
organ does not affect this input.
7
THE HAMMOND ORGAN
- 15-
EXTRA EQUIPMENT
(for organs prior to the -3 series)
HAMMOND ORGAN COMPANY
North Western Avenue - Chicago
Diversey Ave - Chicago
North 25 th Avenue - Melrose Park
Copenhagen Court - Franklin Park
Illinois
USA
ATTACHMENT OF EXTRA EQUIPMENT TO THE HAMMOND ORGAN
INPUT EQUIPMENT
The amplification system of the Hammond Organ may be used as an amplifier for a
microphone, record player, radio or television receiver, or FM tuner. However,
because the amplification section of the instrument is designed for use with the
Hammond Organ generating system, and because organ music is rich in low frequencies,
the bass quality may be abnormally emphasized when such devices are used.
It is sometimes assumed that a high-grade electric organ will necessarily have a
high fidelity sound system. This term, which refers to the ability to reproduce
sound accurately, has no meaning when applied to an instrument which originates its
own sound. Similarly, flat response, which is desirable in a reproducing system, is
not necessarily an advantage in an organ amplifier, where uneven response may be
incorporated intentionally to compensate for opposing variations in the generated
tones.
It should also be noted that reverberation, which is so desirable for organ music,
is less desirable with speech and with some types of music.
For the above reasons it may be found most satisfactory to provide a separate
amplification system, but the suggestions in figures 1 to 6 are furnished in case a
separate amplifier is not available.
NOTES IN REFERENCE TO FIGURES 1 to 6
The volume control shown in these drawings is required because the expression pedal
of the organ does not affect the volume of any attachments. If the record player or
microphone has a built-in volume control, no additional control is necessary.
The . 0005 mfd. condenser and the 1 megohm resistor are a crystal compensating
network and should be omitted if any other kind of microphone or pickup is used.
The voice coil output of a radio or television receiver can be connected in the same
way, except that no additional volume control is required. In case the volume is too
low, it may be necessary to use a suitable step-up transformer.
The output of some FM tuners can be connected in the same way. A volume
control will be required if the tuner does not have its own.
If the organ is to be played at the same time, it should be turned on in the usual
manner. If the organ is not to be played, merely push the run switch
to the on position.
If the organ has a reverberation unit, it should preferably be turned off when using
phonograph or microphone.
Use care in shielding all connections and the volume control, in order to avoid
picking up hum. Make connecting leads as short as possible and expose as little of
unshielded wire as possible.
If the microphone or phonograph does not have enough signal voltage to give adequate
output, a microphone or phonograph preamplifier may be needed in addition.
1
Preamplifier terminal strip
V h. t & 6 & &
.0005 mfd.
1 megohm —
. Crystal microphone
or phonograph
pick-up
k Shielded
wires
/ Remove jumper between n P" and
"Gnd n . Connect inside wire
to W P", connect shield to
"Gnd" .
NOTE: Volume of this type organ will
be reduced somewhat when volume
control is turned up; This
effect can be eliminated by
adding a microphone preamp.
0 — Connect shield to metal case of
— — ^ volume control.
Volume control - 100,000 ohms
FI GORE 1.
Microphone or phonograph connection to tremulant type organs -
Models A, B, BA, BC, C and D
2
NOTE: Later consoles have Radio-Phono
jack on expression control unit of
preamplifier. In this case omit this
condenser and attach shielded wire
directly to plug.
.ore 5 mfd.
1 megohm
asten shield lead
under terminal strip
cover screw
This condenser must be under
terminal] strip cover.
Connect shield to metal case of
volume control.
Volume control - 100,000 ohms
FIGURE 3
Microphone or phonograph connections to selective vibrato organs -
Models B-2, C-2, RT-2
OUTPUT EQUIPMENT
The output of any model Hammond Organ can be connected to earphones, disc and tape
recorder, or broadcast equipment. If necessary, it may be connected to play through
a public address system, although this is generally not desirable. Since so many
types of external equipment are in use, the following general suggestions may have
to be modified somewhat to fit individual cases.
Figures 7 to 10 show various types of output connections.
PLAYING THROUGH EARPHONES
It is important to use only high quality earphones. We recommend the dynamic or
moving coil type, which are quite expensive but give really excellent results. If
the organ is not equipped with reverberation control, crystal earphones will be very
satisfactory if connected as shown in figure 10. On an organ equipped with
reverberation control, the power amplifier connection is best, and good quality
magnetic earphones will give quite satisfactory results. Crystal earphones can be
used in this circuit, but are likely to be less satisfactory than the best quality
magnetic units.
For Home. Church or Concert Model Organ (Models A. AV, B, BA, BC,
BV, BCV, B-2. B-3, C, CV, C-2, D, DV, E, G, GV, RT, RT-2), the preferred
connection is to the power amplifier in the tone cabinet, if the organ is equipped
with reverberation control, since this provides reverberated signal to the
earphones. Refer to figure 7, if tone cabinet is type HR-40 or JR-20, or to figure 8
for other models. If crystal earphones are used, connect a . 1 megohm resistor in
series to avoid excessive high frequencies.
3
If the organ does not have reverberation control it is equally satisfactory, and
often more convenient, to connect to the console preamplifier as shown in figure 9.
If crystal earphones are used with this circuit, connect a . 1 megohm resistor in
series to avoid excessive high frequencies.
Crystal earphones will give better results if connected as shown in figure 10.
RECORDING
Because there are many types and brands of tape, wire, and disc recorders, it has
not been possible for us to test each make and give definite recommendations for
obtaining good recordings. For specific questions regarding connections to your
recorder, we suggest that you contact the manufacturer. Many low-priced recorders do
not reproduce low frequencies well, and this may cause a lack of bass response in
the reproduced organ music. Often the deficiency is chiefly in the playback system
of the recorder, and in this case results will be much better if the organ speaker
or tone cabinet is used for playback.
This resistor con be made
smaller if greater boss
FIGURE 7
Output connections to double channel power a'iplifi p r
4
Switch turns on either
earphones or speaker
FIGURE 8
Output connections to single channel power amplifier
While the microphone supplied with the recorder may be used, best results are
generally obtained by feeding the signal electrically from the organ to the
recorder.
For Connecting Electrically To The Power Amplifier (Home. Church, and
Concert Models A, AV, B, BC, BCV, BV, B-2, C, CV, C~2, D, DV, E, G, GV, RT, RT-2) .
see figure 7, if tone cabinet is type HR-40 or JR-20, or figure 8 for any other type
of tone cabinet. This is the best arrangement if the organ is equipped with
reverberation control, for it provides desirable reverberation in the recorded
music. To play back through the organ speaker, connect the recorder output to the
organ as directed under microphones and record players on a previous page.
For Connecting Electrically To The Preamplifier (Home, Church and Concert
Models) refer to figure 9. This is a convenient pace to make connections if
reverberation is not available or is not desired. With this arrangement, the
recording can be played back through the organ tone cabinet by merely transferring
one wire from the input terminal of the recorder to its output terminal.
For Recording With A Microphone (any organ model), place the microphone at least
several feet from the organ speaker. The quality of the recordings will depend
somewhat on the acoustics of the room, and it will be necessary to experiment with
placement of the microphone to get best results.
5
BROADCASTING
The recommendations above for recording apply also to broadcasting. Feeding the
signal electrically is preferable where possible, and the power amplifier connection
shown in figures 7 and 8 is desirable because it gives the benefit of reverberation.
The voice coil circuits are of 1 to 8 ohms impedance (depending on type of tone
cabinet), with one side grounded and the output voltage is of the order of 1 to 2
volts at normal playing levels. A coupling transformer may be used if it is
necessary to isolate the circuits.
The G to G Connection shown in figure 9 is a 200 ohm circuit with grounded
center tap, and the signal voltage at normal playing levels is of the order of
2 volts.
If microphone pickup is preferred, the usual arrangement is to place a microphone
about three feet above the top of the tone cabinet and inclined at an angle of about
45 degrees. Because types JR-20, H-40, and HR-40 tone cabinets use bass and treble
speakers pointed in different directions, the microphone should be placed at least
10 to 15 feet from cabinets of these types.
CONNECTING TO PUBLIC ADDRESS SYSTEM
It is not recommended that Hammond Organs be connected to play through a public
address system. Most PA systems emphasize the higher frequencies, particularly in
the voice range, and this will result in a serious lack of bass response in the
organ music. In addition, the usual placement of PA equipment, with many speakers
distributed over an area, tends to diffuse the organ music beyond a useful degree.
If it is essential that such a connection be made, use power amplifier output
connections shown in figures 7 and 8.
6
To earphones
To recorder
NOTE: Switch and
resistors are required
only for silencing
tone cabinet.
-Each 500 ohms, £ watt
Switch
Cable wires — ► BK.
Qurtput connections to preamplifier
For tremulant type preamplifier connect to terminal 2 of 56 tube (or
terminal 3 of 6J5 or 6C5 in Model E) . For non-selective vibrato
preamplifier connect to terminal 2 of tube V5. For selective vibrato
preamplifier connect to terminal 2 of tube V3.
.1 meg i w att Jr watt
.02 mfd.
200 volts
Each
:.002 mfd :
200 volt
1 5 meg To
4 watt crystal
, earphones
Preamplifier]
Ground '
-Each 500 ohms, £ watt
Switch
Cable vires
BK I RED
* Circuit for silencing tone
cabinet while earphones
are in use
FIGURE 10
Tone-compensated circuit for connecting crystal earphones to preamplifier
7
CONSOLE HEATER
In very humid climates and in other locations where the Hammond Organ is exposed to
extreme dampness, it is often advisable to install a heater in the console to keep
the interior of the instrument dry and to reduce the possibility of excess moisture
causing damage to electrical parts.
A heater designed for this purpose (was) available In kit form from the factory.
This kit includes all necessary mounting parts and may be installed by the service
technician in any Hammond organ console in a few minutes time.
INSTALLATION OF HEATER IN MODEL A CONSOLES
1. Attach the special bracket furnished with the kit to heater socket as shown
in figure 2, using two screws and lock washers. All mounting holes in the special
bracket are tapped for screws, so no nuts are necessary.
2. Remove back of console and attach heater to flange at upper left hand
corner of rheostat box as shown in figure 2, using the remaining two screws, flat
washers and lock washers furnished with kit.
3. Remove power terminal panel cover and solder heater cord ends to terminals
8 and 13 counting from left of panel as shown in figure 1.
4. Replace terminal panel cover, plug heater in socket and attach red
instruction tag to power cord plug.
INSTALLATION OF HEATER IN MODEL B, C, & D CONSOLES
1. Remove back of console and place heater socket 3 / 4 " to the left of oil cup
mounting plate as shown in figure 3 and mark location of two mounting holes. These
holes should be in line with oil cup mounting screws. (Consoles are now being
furnished with these holes punched in mounting plate. )
2. Drill holes for heater socket mounting, using a #24 or a 5/32 // ’ drill.
3. Drill another similar hole for cable clip 8 3/4 r/ to the left of holes just
drilled and in line with same.
4. Using two of the screws, lock washers and nuts provided with the kit, mount
the heater socket and one cable clip. The clip is held in place by the left hand
socket mounting screw.
5. Mount the other cable clip with the remaining screw and fasten heater cord
in place.
6. Remove power terminal panel cover and solder heater cord ends to terminals
#8 and #13 counting from left of panel as shown in figure 1.
7. Replace terminal panel cover, plug heater in socket and attach red
instruction tag to power cord plug.
8
INSTALLATION OF HEATER IN MODEL E CONSOLE
1. Remove back of console and place heater in position at left end of oil tubs
mounting plate as shown in figure 4 and mark location of two mounting holes. Holes
should be 3/ 16^ from top edge of plate and left hole should be 1/A" from end.
2. Drill holes for mounting heater socket, using a #24 or a 5/ 32^ drill.
3. Using two screws, lock washers and nuts provided with kit, mount heater
socket and one of the cable clips. The clip is fastened by the left hand socket
mounting screw.
4. Mount the remaining cable clip on post supporting run motor oil tube and
fasten heater cord in clips.
5. Remove power terminal panel cover and solder heater cord ends to terminals
#8 and #13 counting from left of panel as shown in Figure 1.
6. Replace terminal panel cover, plug heater in socket and attach red
instruction tag to power cord plug.
POWCR TERMINAL PA.TSC.L_
FISURE1 l.
9
REAR VIEW OF CONSOLE
.WITH back removed
FIGURE 3
location of
HEATER RESISTOR
MODEL E COR SOLE
FIGURE 4.
10
THE TUNING FORK REGULATOR
The Hammond Organ is furnished in several models designed to operate from a closely
regulated 25, 50 or 60 cycle current source. The tone generators are driven by
synchronous motors and any variations in frequency will vary the speed of the motors
and thus the pitch of the instrument. For example, a frequency variation in 60 cycle
current of h cycle is noticeable in the output of the organ, and a variation of as
much as 12 cycles is definitely objectionable.
The tuning fork regulator is a device of our manufacture which is designed to
furnish sufficient closely regulated current of proper frequency to operate the
organ from unregulated AC or converter AC as produced by a DC to AC rotary
converter.
Start motors, preamplifier and power amplifiers are not critical to slight frequency
variations, so when the frequency regulator is used it is connected to furnish
regulated current only to the synchronous run motors.
MODEL G REGULATOR
The Model G regulator is designed for AC operation only, and may be energized by any
23 to 63 cycle line. Current consumption is approximately 125 watts. This must be
taken into consideration when the organ is to be operated from the output of a DC to
AC converter. Failure to provide a converter of adequate size may result in low
line voltage and impaired operation of the instrument.
CIRCUIT
Figure 1 shows a circuit diagram of the regulator. A straight vibrating arm is used,
with push-pull pick up coils and a permanent magnet. The signal is passed through a
push-pull resistance coupled circuit consisting of two 6F5-G tubes and then into two
RK-49 output tubes.
R-42 and R-52 furnish grid bias to the tubes, while R1 provides proper screen
voltage for the output tubes. Oscillation is maintained by a driving coil fed
through a 6C5-G or a 6J5-G tube. (These tubes are interchangeable).
A small neon glow lamp across the output indicates proper operation of the
regulator. Resistor R-33 protects the neon lamp in regulators having 230 volt
output. The output switch connects a power factor correcting condenser in order to
obtain maximum output when two running motors are to be supplied. The power supply
circuit employs a full wave rectifier with a single choke filter and an oil
condenser block.
The 115 and 230 volt models differ in the power transformer and output transformer
used. Power transformers for both voltages have marked taps to compensate for slight
line voltage variation. Models for 50 and 60 cycle output differ only in the
vibrating reed.
Tubes used: 1 5Z3, 2 RK-49, 2 6F5-G, and 1 6C5-G or 6J5-G.
11
NOTE: Model G Regulators of 115 volt - 60 cycle output serial numbered below 1101,
115 volt - 50 cycle below 1060, and 230 volt - 50 cycles below 2059 used two 6L6-G
tubes instead of RK-49s. Also choke LI and resistor R1 were not used, and R52 was
20, 000 ohms.
Lx Ohoka oolX RX-J106
If Ohoka oolX [500 hanrlaa ain.lnduotaaaa.
I 2500 obaa mu. 0.0. Baaiatanoa.
ADJUSTMENT OF PITCH
Adjustment of pitch is possible by moving a weight on the vibrating arm. A single
weight is provided for this purpose. Moving this weight toward the center of the arm
raises the pitch, and moving it toward the end will lower the pitch. The range of
the pitch adjustment is approximately 430 to 460 for middle A (normally 440). This
pitch may be checked by means of a 60 cycle synchronous clock, which is connected to
the regulator receptacle and compared with any other accurate timepiece.
12
If the electric clock checks exactly, the organ pitch will be A 440. A difference of
two seconds in an interval of 14 minutes and 40 seconds will change the pitch one
part in 440. For example, if the synchronous clock indicates 14 minutes and 48
seconds in an actual interval of 14 minutes and 40 seconds, the organ pitch will
be 444 for middle A.
INSTALLATION
In order to use the Model G regulator with an organ, a change in the wiring on the
power panel inside the. console is necessary. This change in power wiring is shown
in figure 2.
VIEW OF LINZ PANEL AFTER CHANGES ARE MADE
FIGURE 2.
These changes are made as follows:
1. Move blue wire from 14 to 13. (Do not make any other changes in 13)
2. Cut out jumper between 8 and 9.
3. Cut out jumper between 12 and 13.
If serial number of Console is below No. 328 it will be necessary to interchange
wires 8 and 9 in order to make revamped panel connections check with diagram shown
above. If serial number is below No. 775 it may also be necessary to interchange
wires 12 and 13.
In addition to above changes, one of the power circuits shown in figures 3 and 4
should be used. Also, the console-to-cabinet cable must be spliced to separate the
power cord as shown in figure 5.
Figure 3 shows a typical installation or the Model G regulator for use on an
unregulated frequency A. C. line.
Figure 4 shows a typical installation where the unregulated A. C. is supplied by a
rotary converter.
In both or these figures, the switch #2 is provided to eliminate undesirable noise
which is introduced through the amplification system if the console is started after
the amplifiers have been turned on. Switches #1 and #2 should both be located near
the console.
13
TO POWER
AMPLIFIER
Figure 3
14
UNREGULATED
TO POWER
AMPLIFIER
FIGURE 4.
15
To start the organ when installed in this manner, the following procedures should be
followed :
1. Turn on switch #1. Watch for the neon lamp on the regulator to glow.
2. Start the console in the usual manner.
3. Turn on switch #2.
A maximum of three amplifiers may be energized through the console to cabinet cable
as shown. If additional cabinets are required they should be connected in the usual
manner to a separate power source.
Switch #2 may be eliminated by including a special relay in series with the
synchronous motors to turn on the power cabinets. Figure 7 shows this relay in use.
This relay does not have sufficient current carrying capacity to control the A. C.
supply to the power amplifiers directly, therefore, it is necessary to also include
a type A-107 relay for this purpose.
Type 3040A5 relay manufactured by the Automatic Electric Company is used in series
with the console run motors, and type A-107 manufactured by the Allen-Bradley
Company is used to energize the power amplifiers.
A convenient method of providing automatic operation is to mount both relays in a
box provided with the necessary fittings to connect to organ equipment and power
source as shown in figure 6. This method is especially useful for demonstration work
as no special wiring is necessary other than the usual changes to console line
panel shown in figure 2.
Such a relay box may be located in any location most convenient for plugging in the
organ equipment. A box 18 inches by 8 inches outside dimensions is a convenient size
as the Model G regulator may then be placed on top of the relay box and the
connections made in an orderly manner. The relay box should be at least 3 'A inches
in depth inside.
16
Floras 5.
P014RI2KD PL DO TO
MODEL 0 REGULATOR
PLOO TO A.O.
SUP PL T
(OEHEOULATZD)
nouRs 6.
17
FIGURE 7*
18
SPEAKER REPLACEMENT IN EARLY TONE CABINETS USING ELECTRODYNAMIC SPEAKERS
CHASSIS
USE SLEEVING
ON THIS LEAD
Electrodynamic speakers are no longer being manufactured. They can be replaced
with Permanent Magnet (PM) speakers in early Hammond tone cabinets. Good results
will be achieved, if the instructions on the next page are followed.
1. Remove speaker plugs from amplifier and remove both speakers from tone cabinet.
2. Clip all 4 wires from both speakers as close to speaker as possible.
3. Discard both speakers.
4. Remove wires from pins 1 and 6 of the 6 pole plug. Remove these wires from
cable.
5. Remove wires from pins 1 and 5 of the 5 pole plug. Remove these wires from
cable.
6. Install a 250 ohm 20 watt resistor across pins 1 and 5 of the 5 pole plug.
Use sleeving over lead connected to pin 5.
7. Solder 2 remaining wires in each speaker cable to the new PM speakers. Solder
wire with solder lug to the left hand speaker terminal as viewed with the
speaker terminal strip facing up. Solder wire from speaker plug to right
hand terminal.
8. Mount new speakers in cabinet and insert plugs into amplifier. Attach leads
with solder lug to upper binding post.
9. Dress 250 ohm resistor away from any speaker leads or other objects to assure
adequate heat dissipation.
19
THE HAMMOND ORGAN
- 16-
WIRING & SCHEMATIC
DIAGRAMS
PART 1 - CONSOLE DIAGRAMS
HAMMOND ORGAN COMPANY
North Western Avenue - Chicago
Diversey Ave - Chicago
North 25 th Avenue - Melrose Park
Copenhagen Court - Franklin Park
Illinois
USA
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FIGURE 22A- WIRING DIAGRAM OF HAMMOND ORGAN CONSOLE MODEL RT-
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THE HAMMOND ORGAN
- 16-
WIRING & SCHEMATIC
DIAGRAMS
PART 2 - CONSOLE
PRE-AMPLIFIERS
HAMMOND ORGAN COMPANY
North Western Avenue - Chicago
Diversey Ave - Chicago
North 25 th Avenue - Melrose Park
Copenhagen Court - Franklin Park
Illinois
USA
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FIGURE 25 - UNDERSIDE OF PREAMPLIFIER -TYPE AO-28
Models B3, C3, RT3, A-100, D-100
THE HAMMOND ORGAN
- 16-
WIRING & SCHEMATIC
DIAGRAMS
PART 3 - POWER & REVERBERATION
AMPLIFIERS IN CONSOLES
HAMMOND ORGAN COMPANY
North Western Avenue - Chicago
Diversey Ave - Chicago
North 25 th Avenue - Melrose Park
Copenhagen Court - Franklin Park
Illinois
USA
WIRING DIAGRAM
AO-39 POWER AMPLIFIER
USED IN HAMMOND ORGAN
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POWER SUPPLY CHASSIS
THE HAMMOND ORGAN
- 16-
WIRING & SCHEMATIC
DIAGRAMS
PART 4 - PEDAL SOLO UNITS
HAMMOND ORGAN COMPANY
North Western Avenue - Chicago
Diversey Ave - Chicago
North 25 th Avenue - Melrose Park
Copenhagen Court - Franklin Park
Illinois
USA
FIGURE 2B
SCHEMATIC -PEDAL SOLO UNIT - TYPE RTB
MODEL RT-2 CONSOLES
NO. 1362 AND ABOVE
YELLOW
REFERENCE SYMBOLS FOR COMPONENTS REFER TO PEDAL SOLO
UNIT SCHEMATIC, FIGURE Z B
FIGURE 4B -UNDERSIDE OF PEDAL SOLO GENERATOR TYPE RTB
YELLOW
REFERENCE SYMBOLS FOR COMPONENTS REFER TO PEDAL SOLO
UNIT SCHEMATIC. FIGURE ZB
F1GURE4C -UNDER5IDE OF PEDAL SOLO GENERATOR TYPE RTC AND ABOVE
REFERENCE SYMBOLS FOR COMPONENTS REFER TO PEDAL SOLO
UNIT SCHEMATIC, FIGURE 2
FIGURE -UNDERSIDE OF PEDAL SOLO CONTROL PANEL
THE HAMMOND ORGAN
- 16-
WIRING & SCHEMATIC
DIAGRAMS
PART 5 - TONE CABINET
PRE, POWER & REVERBERATION AMPLIFIERS
HAMMOND ORGAN COMPANY
North Western Avenue - Chicago
Diversey Ave - Chicago
North 25 th Avenue - Melrose Park
Copenhagen Court - Franklin Park
Illinois
USA
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I ADDITIONAL AMPLIFIERS
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FIGURE I9A- TYPE LR POWER AMPLIFIER
VIEW INSIDE OF CHASSIS
SELECTOR SWITCH
FIGURE I9C -TYPE LR POWER AMPLIFIER
VIEW INSIDE OF CHASSIS
FIGURE 23
INSIDE VIEW OF AO-15 AMPLIFIER
SHOWING LOCATION OF COMPONENTS
FIGURE 23 A
INSIDE VIEW OF AO-15 AMPLIFIER
SHOWING LOCATION OF COMPONENTS
FIGURE 23B
INSIDE VIEW OF AO-15 AMPLIFIER
SHOWING LOCATION OF COMPONENTS
2000CY.FR0M Q1 1062
NOTE: FOR AMPLIFIERS WITH CODE "C" AND ABOVE. REFER TO REVISED SCHEMATIC ON NEXT PAGE.
FIG. 26A AO-33-3 AMPLIFIER USED IN PR-40 AND QR-40 TONE CABINETS FOR AMPLIFIERS CODE "A" & "B."
FIG 27A AO - 33-3 AMPulFli
FIG 28 AO-33-2 AMPLIFIER USED IN PR-20 TONE CABINET
FIG. 28A AO-33-2 AMPLIFIER USED IN PR-20 TONE CABINET
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THE HAMMOND ORGAN
- 17-
TROUBLESHOOTING
HAMMOND ORGAN COMPANY
North Western Avenue - Chicago
Diversey Ave - Chicago
North 25 th Avenue - Melrose Park
Copenhagen Court - Franklin Park
Illinois
USA
THE FOLLOWING INFORMATION PERTAINS SPECIFICALLY TO THE
MODELS B-3 AND C-3. HOWEVER DUE TO THE SIMILARITY OF THE
CONSOLES, MUCH OF THE INFORMATION CAN BE APPLIED TO ALL OTHER MODELS.
SECTION 1 of the original manual was a General Description overview already covered in the 2016
edition and has been intentionally omitted.
PRE-REPAIR PROCEDURES
2-1. POWER REQUIREMENTS.
2-2. POWER SOURCE. For operation, operational tests, and repair procedures, the
Model C-3 Hammond Organ requires connection to a standard 60-cycle, 117-volt (or 50
cycle, 234-volt) power source.
2-3. INSPECTING, STRIPPING, CLEANING, AND LUBRICATING.
2-4. OVERALL INSPECTION.
2~5. Rotate all controls and operate all switches. Pull out all drawbars. Operation
should be smooth. Toggles should snap firmly into position. Depress the playing
keys; check for proper tension in each case and for cracks and chips. Check the
operation of the locking and trip mechanism by striking each preset and adjust
key in turn. Be sure that the cancel key releases the associated preset or adjust
key on each manual.
2~6. Check the mounting of the reverberation spring system assembly in the tone
cabinet. Determine that the locking lever is in its unlocked position; if it is not,
unlock as indicated on instruction card on tone cabinet.
2~7. Insert all connector plugs into their receptacles. Plug should seat firmly and
must make good contact. Inspect all connector plug for loose prongs or pins. Examine
all cords and cables for frayed insulation and defective wiring. Check for kinks,
bends, or twists.
2~8. Inspect all parts and wiring for rust, corrosion, loose connections, frayed or
burned insulation, loose mounting screws and bolts, and burned resistors and coils.
Check and tighten all mechanical fasteners, such as screws and bolts. Make a
thorough inspection of all tube sockets for broken contacts. Examine all switches
for loose or bent contacts and for broken insulation. Inspect spring for proper
tension. Be sure that each end of each spring is properly attached to the associated
parts. Inspect for any broken parts, evidence of excessive heating and overloading,
as indicated by burned resist on or melted wax. Look and smell for these latter
troubles.
2-9. Examine all terminal strips, boards, and panels for defective wiring, broken
lugs, loose contacts, and signs of burning. Be sure that all screws on the preset
panel are securely tightened in position and that all leads are held firmly in
place.
2-10. Push down and raise the swell pedal and note the action of the crank and hinge
assembly. Tighten mounting screws where necessary.
1
2-11. Check the speaker cones for defects. Check the speaker mounting bolts for
tightness.
2-12. Inspect all pedals on the pedal clavier for cracks or breaks and for proper
tension. (Each pedal should just come up when a 3-pound weight is placed directly
behind the pedal sharp cap. ) Be sure that the flat spring pushers at the ends of the
levers are firmly mounted and are properly seated in place over the pedal switches*.
Determine that the felt pad extending over all the plungers is in place and not
worn. Adjustable tension springs are made accessible by removing the cover board
from the rear of the pedal clavier. If pedals become loose and rebound when played
rapidly, increase the tension by tightening the adjustment screws*. (* = Figure 14,
Section 8)
2-13. Check the generator anchoring fittings. They should be unscrewed so that the
generator floats freely. Be sure that all suspension springs for the generators are
connected in position at both ends and are properly positioned.
2-14. Be sure that the console is located on a rigid level surface, so that the
generator mounting mechanism, anchored to the generator frame, is free to move in
any direction without coming in contact with the wooden shelf of the console bottom.
2-15. Be sure that the tone cabinet is located with the open back placed 2 inches or
more from the wall or other obstruction. Be sure that adequate ventilation has been
provided.
2-16. Check all tubes for cracks in glass or base, and for bent or broken prongs.
Inspect for firm mounting of the tubes in their sockets. Test tubes for low
emission, leakage, and short circuits. Test all tubes at least semi-annually and
replace them at least every 18 months. Inspect pins and bases for accumulations of
foreign matter.
2-17. As the Model C~3 Hammond Organ is used in chapels and auditoriums, it is
unlikely that inspection will find the organ deteriorated beyond repair, except
where it has been subjected to fire or explosion.
2-18. REMOVAL AND REPLACEMENT OF PLUCK-OUT PARTS.
2-19. VACUUM TUBES. The following instructions apply when it is necessary to remove
and replace vacuum tubes.
a. Table I lists the tube complement of the Model C~3 Hammond Organ and Model
PR-40 Tone Cabinet.
b. Never remove tubes from the amplifiers when the organ is turned on. Avoid
working on the tubes immediately after shut-down; severe burns may result from
contact with the envelopes of hot tubes. Never jar a warm tube.
c. When replacing a defective tube, do not jiggle the tube from side to side in
its socket. Movement of the tube weakens the pins in the base and unnecessarily
spreads the contacts in the socket. Replace the defective tube; be sure that the
replacement is pressed down firmly in its socket.
2
TABLE 1
Unit
Tube
FTnrnrnHi
Unit
Tube
Quantity
Console Preamplifier
6AU6
2
Power Amplifier
2
6C4
2
(in PR-40 Tone Cabinet)
6AU6
2
6X4
i
6BQ5
6
i
12AU7
1
SEJtl
i
12AX7
2
12BH7
i
12BH7
1
2-20. PEDALCLAVIER. The following instructions apply when necessary to remove and
replace the pedalclavier.
a. Remove the bench positioned over the pedal clavier.
b. Lift the console end of the pedal clavier and pull slightly up and out.
c. To replace the pedal clavier, place it in position, lifting slightly at the
front, and slide it under the console until it locks in place. Place the bench in
its proper position over the foot pedals.
2-21. CORDS AND CABLES. Disconnect cords and cables by firmly grasping the connector
plug and pulling it.
2-22. CLEANING.
2-23. The following materials are required to perform cleaning operations on the
Model C-3 Hammond Organ:
a. Clean cloth.
b. Dry-cleaning solvent.
c. Paint brush with camel’ s hair bristles.
d. lint-free, bleached cloth
e. Compressed air.
f. Crocus cloth.
2-24. Remove corrosion, rust, or dirt. Blowout dirt and dust from the interior of
the console and the tone cabinet. If an air hose is used, be sure that any water
which may have condensed in it is blown out before applying the air stream to the
equipment. When using compressed air to remove dirt, be careful not to disturb the
wiring. Scrape off tar or other adhering foreign matter; touch up with paint or
lacquer if necessary.
2-25. Clean the vacuum tube sockets and pin receptacles with solvent and a camel’ s
hair brush. If necessary, clean pins with crocus cloth.
2-26. Clean all wooden parts and playing keys with a clean, lint-free cloth.
Accumulations of dirt and dust in the key contacts may be removed by adjusting the
bus bar shifters. (See paragraphs 4-9 to 4-13 inclusive. ) No disassembly
is required.
3
2-27. LUBRICATION
2-28. APPROVED LUBRICANTS. The following listed lubricating material is required to
service the Model C~3 Hammond Organ: Spec MIL-L-644
2-29. CONSOLE. Some moving parts receive lubrication by capillary action via cotton
threads connected to the central oil trough. Oil is fed to this trough from two oil
cups (See picture on page 1 of Main Generator section). To pin access to these oil
cups, remove the rear dust panel by unscrewing the two thumb screw bolts. Every year
fill the oil cups three-quarters full with oil, Spec MIL-L-644. (The oil level will
slowly drop; however, do not continue adding oil.)
2-30. INSPECTING AND TESTING REMOVED PARTS.
2-31. VACUUM TUBES.
2~32. INSPECTING. Check each tube for tight mounting in its socket. Inspect visually
for mechanical and other obvious defects. Discard defective tubes. Be certain that
each tube is of the type specified.
NOTE
Return each tube, if found to be good, to the socket from which it was removed.
Distortion will result if replaced tubes are mismatched.
2~33. TESTING. Use tube checker in accordance with the instructions furnished. Do
not neglect the short circuiting test.
2-34. CABLES AND CONNECTORS.
2~35. INSPECTING. Inspect cables for cracked, frayed, or deteriorated insulation at
the connecting or supporting points. Inspect the cables or connectors for improper
placement which puts them under strain. Watch for kinks and improper supports.
Inspect all connectors for dirt, corrosion, and damaged or loose contacts or
terminals. To prevent possible short circuits, be sure no corrosion or dirt remains
between the contacts.
2~36. TESTING. Use an ohmmeter and make continuity checks on the cables. Test for
grounding and for shorting between points; if defects are discovered in connectors,
replace the connectors. Test the voice coils. Reading of approximately 8 ohms should
be obtained.
TROUBLE LOCATION
3-1. TROUBLESHOOTING.
3-2. GENERAL. When troubleshooting, use all of the aids included in this manual:
block diagrams (see General Descriptions), overall schematics, amplifier schematics
(see Wiring and Schematic Diagrams), illustrations of components (throughout
manual), and the trouble shooting chart (reference paragraph 3-28). Before starting
an elaborate test procedure, make a thorough visual inspection to locate the fault.
Check for defective wiring, drops of solder, faulty connections, open resistors
and capacitors, jammed tone wheels, etc.
4
3~3. TUBE TESTING. When the trouble is traced to a specific stage, test tubes in
that stage. If tubes are satisfactory, make a point-to-point voltage check in
accordance with paragraph 3-4.
3~4. VOLTAGE AND RESISTANCE MEASUREMENTS. Make voltage and resistance measurements
on the individual components of the stage (as shown in specific console schematic).
Make all capacitor checks with capacitor analyzer if available. Always disconnect
capacitors before making tests; otherwise the readings will be affected by a
possible shunt circuit. Replace any capacitor which shows a deviation of 20
percent or more.
3~5. RESISTORS. Resistors used in Hammond Organs are marked with the standard EIA
(Electronic Industries Association) color code, as shown in Table II. In this code,
the body color or first color ring (starting from the outside edge) indicates the
first digit of the resistor value. The second ring denotes the second digit, and the
third ring represents the number of zeros after the second digit. Thus a resistor
marked with brown, green; and yellow rings (in that order) would have a value of
150,000 ohms. Gold and silver rings represent percentage tolerance, gold indicating
5 percent tolerance and silver indicating 10 percent tolerance. Replace resistors
differing by as much as 30% from their rated values.
TABLE II-
RESISTOR COLOR CODE
0-Black
4-Yellow
1 -Brown
5-Green
2-Red
6-Blue
8-Gray
3-Orange
7-Violet
9-White
3~6. COIL MEASUREMENTS. For the DC (direct current) resistance value of chokes and
audio transformers, refer to the appropriate circuit diagram. An open winding in the
choke or transformer will be indicated by no ohmmeter indication. Check the power
and filament transformers by comparing their measured voltage with the voltages
given in the circuit diagram. All voltage values are given for a 117- volt (or
234-volt) AC input. If the input voltage varies, a corresponding change will be
noted.
3-7. SECTIONALIZING TROUBLE
3-8. AMPLIFICATION SYSTEM TROUBLES.
3~9. Such troubles as loss of volume, poor quality, excessive hum, noisy operation,
or no signal are usually traceable to the amplification system. For example, if
distortion is noted in the loud speakers, connect a headset across terminals marked
G - G on the console preamplifier. If the quality is good on the headset, the cause
of the distortion will be found in the amplification system following the console
preamplifier. Should distortion occur at the preamplifier terminals, replace all
tubes. Should distortion in the console preamplifier continue, test each
preamplifier stage individually with the headset. When the defective stage is
located, test each capacitor and resistor for deterioration.
5
CAUTION: Insert an 0. 1 mfd, 400 volt DC capacitor in series with the headset to
prevent DC voltage from damaging it.
3-10. HUM.
3-11. Hum in the loud speakers may indicate trouble in the reverberation spring
system assembly. (Reference paragraph 3-28. ) If a sustained hum or howl is heard,
starting only when a low note is played at high volume, check for
the following:
a. Microphonic tubes in the amplifier. Replace all tubes if necessary.
b. Improper grounding of all plug connections to and from the amplifier.
c. Defective bypass capacitors in the reverberation portion of the amplifier.
d. Locked spring system.
e. Improper mounting of the reverberation unit.
f. Presence of undesirable magnetic fields, such as motors, generators, supply
transformers, and other equipment generating heavy magnetic field patterns.
3-12. LOCATING AND CORRECTING DEFECTIVE INDIVIDUAL TONES.
3~13. Silent or weak individual tones are usually caused by defects in the circuit
ahead of the amplification system. Such defects can be traced to the tone generator
and filter circuits, key circuits and board connections, and signal wiring between
the manual chassis, generators, and pedal switch. Trouble occurring over the full
range of tones and present at the input to the console preamplifier can usually be
traced to a defect in the mixing transformer or associated circuitry.
3-14. LOCATING DEFECTIVE TONES.
3~15. Depress preset key A# on the upper manual. (See figure 1 in Manuals, Pedals,
etc. )
3-16. Pull out the first (No. 1) brown drawbar only in the first set of drawbars in
the left-hand group.
3-17. Start with the first key, C, (frequency No. 13) of the upper manual and strike
each higher note on this manual in succession. The last note at the right end of the
keyboard is C (frequency No. 61). Note the frequency numbers of all weak or dead
notes. Figures 4 (p. 5) & 13 (p. 15) in Manuals, Pedals, etc. indicates all key
numbers and notes and the corresponding frequency numbers for each drawbar.
3~18. Return the first brown drawbar to its original position and then pull out the
last white drawbar only, in the same draw bar set. (Reference paragraph 3-16. ) Start
at the second C note (frequency No. 61), and strike each higher note on the upper
manual in succession until the second F# note from the top of the keyboard is
reached. This F# note corresponds to frequency #91, the highest frequency produced
by the generator. Note the frequency number of all weak or dead notes.
6
3~19. Repeat the procedures of paragraphs 3—15 to 3—18 inclusive, on the lower
manual. Use the No. 1 brown and No. 9 white drawbars in the first set of drawbars in
the right-hand drawbar group.
3~20. If all notes are uniform in intensity or change evenly from note to note, the
tone generators are operating normally. However, if notes are weak or absent,
proceed as directed in paragraph 3-21.
3-21. CORRECTION.
3~22. A single dead or weak note which occurs on one manual but not on the other,
may be caused by a fault in the key contacts. To correct this fault, adjust the bus
bar shifters associated with the pedal switch and both manuals as directed in
paragraphs 4-9 to 4-13 inclusive.
3~23. A single weak or dead note occurring at the same point on both manuals may be
caused by a defective generator, a broken wire, or a poorly soldered joint on the
terminal strip. Test the generator for output by fastening a short length of wire to
the 6th busbar, from the bottom, on the preset panel; then touch the other end of
the wire to each lug on the generator terminal strip. If all notes sound, the cable
wire or soldered joint is at fault and must be repaired. If no generator output
exists, either the filter circuit or the magnet pickup coil may be defective, or the
tone wheel is not rotating.
3~24. Figures 5 & 6 in the Main Generator section illustrates the position of each
filter reactor and capacitor on the generator cover. Fasten a short piece of wire to
the 6 lh busbar from the bottom, on the preset panel, and test each terminal of the
filter. (Reference paragraph 3-23. ) If the filter is at fault, replace the defective
component as described in paragraphs 5-86 and 5-87.
3~25. If there is no signal across the magnet pickup coil terminals, even with the
coil disconnected, either the coil is defective or the associated tone wheel is not
turning. Check the pickup coil by unsoldering its lead and, with a short piece of
wire, connect the lead to the preset panel. (Reference paragraph 5-6. )
3~26. When there are two dead notes on each manual, determine which frequencies are
at fault, as described in paragraphs 3-14 to 3-20 inclusive. Figure 4 in the Main
Generator section illustrates the exact location of the magnet associated with each
frequency; the dotted lines connecting the frequency numbers indicate that they are
generated by two tone wheels on the same shaft and in the same compartment. (It
should be noted that with few exceptions, tone wheels on the same shaft differ in
frequency numbers by 48.) On frequency numbers 37,38, 39,40, and 41, only a single
active tone wheel is on each shaft. If the 2 magnets associated with the dead notes
are together, 1 tone wheel is probably jammed against the magnet tip. To correct
this condition, proceed as follows:
a. Loosen the set screw on the magnet to be adjusted, then move the magnet
back slightly. Do not twist it.
b. Strike the proper playing key. The note should now sound.
7
c. To make the final adjustment, strike and hold down the playing key for the
note being adjusted. Then tighten the magnet slightly in position and tap it gently
until it moves close to the tone wheel to bring the intensity up to the intensity of
the adjacent notes. Tighten the set screw so that the magnet is held firmly in
position.
d. Do not remove main tone generator assembly from the console unless
absolutely necessary. Should this be necessary, proceed as directed in paragraphs
5—63 to 5~71 inclusive.
3-27. TROUBLESHOOTING CHART.
3~28. The following troubleshooting chart contains general information to aid in the
location of trouble. When the trouble stage is sectionalized, refer to Section V for
detailed aid in identifying the trouble with a particular part.
SYMPTOM PROBABLE CAUSE OR REMEDIAL ACTION
1 . No Signal Check the source of supply ; a 1 1 7-volt, 60-cycle
(or 234-volt, 50-cycle), AC power source is re-
quired. Check the power and connecting cables
for secure mounting, good contact, and broken
pins. Check the power supply voltage in the tone
cabinet. Check all vacuum tubes.
Connect output meter across the console pre-
amplifier output terminals. If no output is ob-
tained, conduct a point-to-point voltage test on
the defective unit.
Check the signal input to the power amplifier
and compare the reading with the console pre-
amplifier output reading on the output meter.
These should be identical. If no output reading
is obtained, conduct a point-to-point voltage
test on the defective unit.
Check the power amplifier output. If no output
reading is obtained, conduct a point-to-point
voltage test.
2. Loss of Volume, All Notes Low voltage, source of supply.
Check the console preamplifier output voltages.
Check the power amplifier output voltages.
Check all vacuum tubes. (Reference paragraph
3-3.)
Low voltage from power supply.
Conduct a point-to-point voltage test and check
for defective components.
3. Loss of Volume, Single Note Dust or accumulation of dirt on contact; make
adjustment. (Reference paragraphs 4-9 to 4-13
inclusive.)
Poorly soldered connection or high resistance
contact in console wiring. Trace the signal in-
tensity throughout the circuit by means of
high-impedance headset (circuit to ground). As
an alternative method, attach one end of an
insulated test lead (48 inches long) to 6th bus
bar from bottom, on preset panel, and use other
lead end to trace the signal intensity throughout
the manual wiring.
4. Poor Quality
S. Excessive Hum
6. Rattle or Intermittent Operations
7. Miscellaneous
a. Howl, or unwanted sustaining of tone
b. Bass pedals release sluggishly . . .
c. Preset keys fail to release properly
Use low volume, and check the console pre-
amplifier output with high impedance headset.
Check all vacuum tubes.
Make a point-to-point voltage test. (Reference
paragraph 3-4.)
Check individual components for defects, espec-
ially audio bypass capacitors and frequency
filters.
Be sure that the voice coils are not nibbing
against pole pieces.
Check all connecting plugs for loose connections.
Check wiring connections in cable plugs.
Check for defective filter capacitors in power
amplifier.
Check all vacuum tubes. Replace if necessary.
Remove all inductive electric or electronic
equipment in the vicinity of the console cabinet
Check all bypass capacitors, particularly on
cathode-to-ground circuits.
Check ground connection from generator to two
halves of lowest preset panel bar.
Loose connections between cable connectors.
Loose cable connections in connector plugs.
Damaged speaker cone.
Voice coil rubbing on pole piece.
Defective vacuum tube.
Check lubrication.
Check the individual felt pad used on each manual
key or bass pedal to absorb the striking sound.
Check for intermittent resistors or capacitors by
lightly tapping suspected components.
Check the suspension of the reverberation spring
system assembly.
Adjust the bus bar shifters. (Reference para-
graphs 4-9 to 4-13 inclusive.)
Check reverberation unit locking lever. (Refer-
ence paragraph 2-6.)
Check and increase tension of leaf springs at end
of bass pedals.
Replace leaf bracket and associated leaf spring;
replace key if necessary. Reference paragraphs
5-73 to 5-75 inclusive
ALIGNMENT PROCEDURES
4-1. PRESET PANEL TONE SELECTION.
4~2. The preset keys shown in figure 1-2 are used to select the ready-mixed tone
colors. Nine color-coded wires from each preset key are fastened to the busbars of
the preset panel by slotted screws. Each group of nine color-coded wires is fed
through individual holes below the preset panel. The color coding of each group is
identical to the color coding of the nine wires from the drawbars (above the preset
panel). The drawbars can be withdrawn to numbered stops. The frequency relationship
of the wire color coding is indicated below. Note that the color sequence is the
same as the EIA color code for resistors.
Brown Sub-fundamental
Red Sub-3rd harmonic
Orange Fundamental
Yellow 2nd harmonic
Green 3rd harmonic
Blue 4th harmonic
Violet 5th harmonic
Gray 6th harmonic
White 8th harmonic
4~3. The tone color or quality of any note, played on either the upper or lower
manual, is determined by the intensity of the harmonics in relation to the
fundamental note as selected either by the preset key or drawbars. The numbers of
the preset panel and drawbars indicate a progressive increase in intensity, starting
from 0 (drawbar fully pushed in) to 8 inclusive. Any tone color may be identified by
a number containing 9 digits, each digit representative of the intensity of the
fundamental tone or 1 harmonic as selected on the drawbars or preset panel.
4~4. The Hammond Organ has its preset panel arranged to make available to the
organist tonalities similar to those ordinarily found in the small church or chapel
pipe organ, as well as tones for religious services and congregational singing,
without the use of the adjustable drawbars. Table IV illustrates the approved preset
panel arrangement for chapel organs. Remove the rear panel of the console, examine,
and check the preset panel to determine that the preset panel corresponds exactly to
Table IV. Change the position of any lead by loosening the slotted screw which
secures it in place, removing the lead, and then securing it in correct position by
means of the slotted screw provided. Refer to console wiring diagrams.
10
TABLE IV - HAMMOND ORGAN PRESET DATA
UPPER MANUAL
LOWER MANUAL
Preset Keys
Equivalent
Drawbar Setting
Tone Quality
Value
Preset Keys
Equivalent
Drawbar Setting
Tone Quality
Value
C
Cancel
C
Cancel
c#
005320000
Stopped Flute
PP
C#
004545 440
Cello
mp
D
004432 000
Dulciana
PPP
D
004423 220
Flute & String
mp
D#
00 8740 000
French Horn
mf
D#
007373 430
Clarinet
mf
E
00 4544 222
Salicional
PP
E
004544220
Diapason, Gamba and Flute
mf
F
00 5403000
Flute 8’ & 4’
P
F
006644 322
Great, no reeds
f
F#
004675 300
Oboe Horn
mf
F#
005642 200
Open Diapason
f
G
00 5644 320
Swell Diapason
mf
G
00 6845 433
Full Great
ff
G#
00 6876 540
Trumpet
f
G#
008030000
Tibia Clausa
f
A
32 7645 222
Full Swell
ff
A
42 7866 244
Full Great with 16’
fff
A#
Adjust harmonic drawbars for 1st
Group, Upper Manual
A#
Adjust harmonic drawbars for 1st Group, Lower
Manual
B
Adjust harmonic drawbars for 2nd
Group, Upper Manual
B
Adjust harmonic drawbars for 2nd Group, Lower
Manual
4-5. ALIGNMENT OF COIL ASSEMBLIES.
4~6. Each magnet and coil for each tone wheel is mounted in the tone generator as a
single assembly. (See figures 2 & 3 in Main Generator section. ) To locate and
determine which coil assemblies require alignment, proceed as follows:
a. Remove the console rear panel.
b. Connect an output voltmeter (1, 000 ohms per volt scale) across the two
terminals marked G.
c. Set both the vibrato controls, and all percussion tablets, to their OFF
positions.
d. Depress the swell pedal to the position of maximum volume.
e. Disconnect tone cabinet from console.
f. Connect one end of a test lead to the 5 th preset panel busbar, from the
bottom.
g. Place the organ in operation.
h. Check the AC input voltage at the console preamplifier terminal board;
the voltage should be 117 volts or 234 volts. Any variation of input supply voltage
will give a corresponding increase or decrease of reading, as shown in
Table V.
i. Check the output voltage of each coil assembly by touching the prod end
of the test lead to each terminal in turn on the main generator terminal board. The
frequency numbers are not indicated. For location of exact frequency, see figure 5
or 6 in the Main Generator section.
j. Compare each voltage obtained with the appropriate voltage listed in
Table V. Do not try to adjust to these voltages unless the values deviate more than
30 percent.
11
4~7. If it is ascertained that the coil assemblies require alignment, proceed as
follows :
a. Disconnect the generator assembly only when absolutely necessary. Make
adjustments from the rear whenever possible. Do not remove the cover as this
necessitates unsoldering and resoldering 91 leads, in addition to realigning all
coil assemblies.
b. Refer to figure 4 in Main Generator section and determine which coil
assemblies require alignment.
c. Loosen the set screw which holds the coil assembly in position.
d. Compare the intensity of the note associated with the aligned coil with
the intensity of adjacent notes.
e. Tap the coil assembly gently until it moves close enough to the tone
wheel to bring the intensity up to the intensity of the adjacent notes; pull coil
assembly back if necessary. Do not turn magnet during this operation.
f. Tighten the set screw.
CAUTION:
These coil assemblies are locked into position
at the factory and seldom require
adjustment. Do not pull back with a twisting
motion, as damage will result.
TABLE V
GENERATOR OUTPUT VOLTAGES
Freq.
No.
Output
(V)
Freq.
No.
Output
(V)
Freq.
No.
Output
(V)
Freq.
No.
Output
(V)
1
9.8
23
IS
45
2.7
67
1.2
2
11
24
14
46
2
68
1.6
3
11.5
25
11.5
47
2.5
69
2
4
12
26
12
48
2
70
1.6
5
13
27
10
49
2.25
71
2
6
14
28
11
50
3
72
1.4
7
15
29
10
51
1.5
73
1.4
8
15
30
10
52
2
74
1.2
9
16
31
11
53
1.8
75
1
10
15
32
8.5
54
1.8
76
1.2
11
16
33
10
55
1.8
77
1 |
12
13
34
9
56
1.8
78
1.2
13
14.5
35
10
57
2
79
0.8 ;
14
15
36
8
58
1
80
0.6
15
14
37
9.5
59
1.8
81
0.7
16
15
38
10
60
1.5
82
0.4
17
14
39
9
61
3
83
0.6
18
15
40
10
62
3
84
0.5
19
15
41
8
63
2
85
0.7
20
16
42
9
64
2.5
86
0.5
21
15
43
9
65
2.2
87
0.3
22
13
44
2.5
66
3
88
0.4
89
0.2
90
0.5
91
0.25
12
4-8. ADJUSTMENT OF PERCUSSION CUTOFF CONTROL. This control, located in the
preamplifier (See figure 1-7) should be readjusted whenever control tube V7 is
replaced. Set expression pedal wide open, both volume tablets to Normal, percussion
tablet ON , and harmonic selector in either position. Play any key in upper half of
upper manual, hold it down at least 5 seconds, and then adjust percussion cut-off
control exactly to the point where the signal becomes inaudible.
4-9. ADJUSTMENT OF INTERMITIENT OR NON-OPERATING KEYS.
4~10. Scratchy, noisy, or silent keys may result from accumulations of dust which
lodge in the contacts. To correct this condition, strike the key 15 to 20 times in a
rapid staccato manner to dislodge the dust particles and to clear the contacts.
4-11. If this procedure does not dislodge the dust particles, adjust the busbar
shifters. (See Rear View of consoles at end of General Descriptions, figure 21 in
Manuals, Pedals, etc. , and figures 4-2 & 4-3 below) Busbar shifter A, located behind
the matching transformer, adjusts the busbars associated with the keys of the upper
manual; busbar shifter B adjusts the busbars associated with the keys of the lower
manual; busbar shifter C adjusts the busbars associated with the pedal keyboard.
4-12. Turn the proper busbar shifter about two turns in either direction. This
operation permits the key contacts to strike a new position on the busbar and should
free all contacts of accumulated dust particles.
4~13. If, in extremely stubborn cases, the procedure above does not dislodge the
dust particles, use a board to depress one octave of notes (7 white and 5 black
keys) and then adjust the bus bar shifters while holding the keys down. *
* - this procedure has been deemed inappropriate in recent years and could cause damage to
the key contacts - JL
Figure 4—2. Manual Assembly, End View
PEDAL SWITCH CABLE
(TO GENERATOR TERMINAL STRIP)
RESISTANCE WIRES
(FROM SWITCH CONTACTS TO TERMINALS)
Figure 4—3. Pedal Switch Assembly, Cover Removed
13
STAGE DATA AND FINAL TESTING
5-1. DETAILED THEORY OF OPERATION.
5-2. MAIN TONE GENERATOR ASSEMBLY.
5~3. The main tone generator assembly consists principally of 48 rotating
sub-assemblies (each subassembly consists of a shaft, 2 disks called tone wheels,
and a bakelite gear), and a drive shaft which extends the entire length of the
generator. This drive shaft is resiliently coupled at one end to a starting motor
and at the other end to a synchronous run motor (reference paragraph 5-12), and is
divided into several sections connected by semi-flexible couplings. A series of 24
driving gears, 2 each of 12 sizes, is mounted on this shaft.
5~4. Twenty-four of the 48 rotating subassemblies are mounted on each side of the
drive shaft so that each of the driving gears engages 2 bakelite gears associated
with opposite rotating subassemblies. These bakelite gears rotate freely with the
tone wheels on separate shafts and are connected to their respective assemblies by a
pair of compression-type springs. The bakelite gears are provided in 12 different
sizes corresponding to the 12 driving gears of different sizes. Consequently, 4 of
the tone wheel subassemblies, each containing 2 tone wheels, operate at each of 12
different speeds. Each driving gear, with its associated bakelite gears and 4 tone
wheels, is contained in a separate compartment, magnetically shielded from the rest
by steel plates which divide the generator into a series of bins. (See figure 5-2
on next page). All four tone wheels in anyone compartment run at the same speed.
5-5. Each tone wheel is a steel disk about 2 inches in diameter and contains a
predetermined number of high and low points on its outer edge. (See figures 2 & 3 in
Main Generator section. ) Each high point is called a tooth. There are 12 wheels with
2 teeth, 1 wheel to operate at each of the 12 speeds (reference paragraph 5-4) ;
similarly 12 wheels each have 4 teeth, 8 teeth, 16 teeth, 32 teeth, 64 teeth, and
128 teeth; also 7 tone wheels have 192 teeth. A 2-tooth wheel and a 32-tooth wheel
form an assembly, giving 2 frequencies, 4 octaves apart. The 4- and 64-tooth wheels
are assembled together, as are the 8- and 128- tooth wheels and the 16- and
192-tooth wheels. Five 16-tooth wheels are mounted with blanks to maintain the
balance of the rotating unit. (See figure 5-2 on next page. ) Only 91 frequencies are
required for the organ; for identification purposes these frequencies are numbered 1
to 91 inclusive.
14
4 AND 64
16 AND BLANK
4 AND 64
16 AND 192 —
4 AND 64 —
16 AND BLANK
4 AND 64
4 AND 64
16 AND BLANK
4 AND 64
16 AND BLANK
4 AND 64
16 AND BLANK
4 AND 64
NOTE:
NUMBERS REFER TO
THE NUMBER OF
TEETH ON EACH
TONE WHEEL.
Figure 5—2. Tone Wheel Tooth Count in Generator
15
5~6. A magnetized rod, about 4 inches long and 1/4 inch in diameter, is mounted near
each tone wheel. (See figures 5-1 and 5-2. ) A small coil of wire is wound near one
end of the magnet. The tip of the magnet at the coil end is ground to a sharp edge
and mounted near the edge of the associated tone wheel. Each time that a tooth of
the wheel passes the rod, the magnetic circuit changes and a cycle of voltage is
induced in the coil. The voltage is very small and is of known frequency. The
frequency is predetermined by the number of teeth and the speed of the rotating
tone wheel. Larger coils are used with tone wheels of lower frequencies to provide
good low frequency output, but smaller coils are used with tone wheels of higher
frequency to prevent excessive losses.
5-7. Copper rings are mounted on certain low frequency coils for the purpose of
reducing harmonics. The eddy current loss in such a ring is small for the
fundamental frequency of the coil, but is high for its harmonics. As a result, the
the relative intensities of any harmonics which may be produced by irregularities in
the tone wheels are reduced.
5-8. The edge of each tone wheel and the tip of each magnet are coated with lacquer
to prevent corrosion, for, should oxidation set in, the change in tooth shape would
introduce undesirable frequencies.
5~9. Filters for eliminating spurious harmonics from the generated simple tones are
located on the top of the main tone generator, and consist of filter capacitors and
reactors. (See figures 5 & 6 in the Main Generator section. ) (These capacitors and
reactors are tuned units and are called tone generator filters.)
5—10. The tone generator filters have a single tapped winding. This tap is grounded
and one side, which is connected to the associated coil assembly through a
capacitor, forms a resonant circuit for the fundamental frequency of that coil.
Harmonics are suppressed. The capacitors for frequencies 49 to 54 inclusive are
0. 255 mf, and the capacitors for frequencies 55 to 91 inclusive are 0. 105 mf. Both
capacitors and reactors are used with frequencies numbered 49 to 91 inclusive. On
frequencies 44 to 48 inclusive, the capacitors are omitted, but the reactors used
have a greater number of turns. Below frequency 44, neither capacitors nor reactors
are used; a length of resistance wire shunts each generator output. This resistance
wire is wound on the appropriate magnet coil.
5-11. The tone generator filters are mounted on top of the generator at an angle to
minimize reaction between them. Wires connect the filters to the coil assemblies and
to the terminal strip on the generator. Ninety-six terminals are provided on this
strip; 3 terminals are grounded to the generator frame and serve to ground the
manuals and pedals, and 91 terminals carry the various frequencies.
16
5-12. The start motor is a shaded-pole induction motor. The synchronous run motor
(used on 60 cycles) has a 2-pole field and 6-pole armature, and a synchronous speed
of 1,200 rpm (revolutions per minute). For 50 cycles, a 4-pole armature is used
which has a speed of 1, 500 rpm. When the organ is placed into operation, the start
switch is first operated to apply power to the start motor. The rotor of the start
motor slides endwise and engages a pinion on its shaft which a gear on the generator
drive shaft. (See figure 5-3 below. ) When the RUN switch is operated, while the
start switch is held in ON position, power is applied to the synchronous run motor
and a 250-Ohm resistor (1,000 ohm for 234 volts) is connected in series with the
start motor, thus reducing the driving power of the start motor. Because of the
braking action and the loss of power of the start motor, the system slows down to,
and locks into, synchronous speed; the run motor then begins to carry the load. When
the START switch is released and springs back into position, the start motor
disengages from the drive shaft by action of a spring assembly, and stops.
5~13. The spring couplings of the motor shaft, the flexible couplings between the
sections of the drive shaft, and the tone wheel spring couplings are provided to
absorb the variations in motor speed. The synchronous motor operates with a series
of pulsations, one each half-cycle. If the tone wheels were coupled rigidly to the
motor, this irregularity would carry extra frequencies into each tone wheel. The
spring suspension system for supporting the main tone generator minimizes the
transmission of mechanical vibration between the console cabinet and the main
generator.
WICKS
Figure 5— 3. Starting Motor
17
5-14. VIBRATO EQUIPMENT.
5-15. The vibrato effect is created by a periodic raising and lowering of pitch, and
thus is fundamentally different from a tremolo or loudness variation. It is
comparable to the effect produced when a violinist moves his finger back and forth
on a string while playing, varying the frequency while maintaining constant volume.
5~16. The Hammond Organ vibrato equipment, as shown in simplified block diagram,
figure 1 in the Vibrato and Percussion section, varies the frequency of all tones by
continuously shifting their phase. It includes a phase shift network or electrical
time delay line, composed of a number of low pass filter sections, and a capacity
type pickup or scanner, which is motor driven so that it scans back and forth along
the line.
5~17. Electrical waves fed into the line are shifted in phase by each line section
(the amount per section being proportional to frequency), so that at any tap on the
line, the phase is retarded relative to the previous tap.
5~18. The scanning pick-up traveling along the line will thus encounter waves
increasingly retarded in phase at each successive tap, and the signal it picks up
will continuously change in phase. The rate at which this phase shift occurs
will depend on how many line sections are scanned each second.
5~19. Since a cycle is equivalent to 360 electrical degrees, a frequency shift of 1
cycle occurs for each 360 electrical degrees scanned per second. For example, if the
scanner passes over the line at such a rate that 3,600 electrical degrees are
scanned each second, there will be a frequency change of 10 cycles.
5~20. For the widest vibrato, the whole line is scanned from beginning to end in
about 1/14 second, and this rate of change of phase causes about 1-1/2 percent
decrease in frequency. Note that the frequency remains constantly 1-1/2 percent low
as long as the moving pick-up retards the phase at a constant rate.
5~21. Since the pick-up sweeps from start to end of the line and then back, it
increases the frequency by an equal percentage on its return trip, the average
output frequency remaining equal to the input frequency. The exact amount of
frequency shift depends not only on the amount of phase shift in the line but also
on the scanning rate. This rate, however, is constant because the scanner is driven
by the synchronous running motor of the organ.
5~22. The degree of vibrato (or amount of frequency shift) may be varied by a switch
which causes the whole line to be scanned for No. 3 (wide) vibrato, about half of it
for No. 2, and about one-third for No. 1.
18
5-23. A vibrato chorus effect, similar to the effect of 2 or 3 slightly out-of-tune
frequencies mixed together, is obtained when the vibrato output signal is mixed with
a portion of signal without vibrato. For vibrato chorus, part of the incoming signal
appears across the vibrato line and the rest across a resistor in series with the
line. As the vibrato effect is applied to the part of the signal appearing across
the line, but not to the part appearing across the resistor, the combination
produces a chorus effect. For normal vibrato, this resistor is short-circuited. In
the Model C~3 console the vibrato effect can be applied to either manual separately
or to both at once.
5~24. Figures 2, 3, & 3a in the Vibrato and Percussion section shows the vibrato
line box. Each of the inductance coils is connected with one or more capacitors to
form one filter section.
5~25. Figure 4 in the Vibrato and Percussion section shows the construction of the
vibrato switch.
5~26. The scanner, shown in figure 5 of the Vibrato and Percussion section, is
mounted on the main generator synchronous motor and driven at 412 revolutions per
minute. It is a multi-pole variable capacitor with 16 sets of stationary plates and
a rotor whose plates mesh with the stationary ones. In Index B of the same figure,
two sets of plates have been removed to show the rotor.
5-27. Signals coming from the line through the vibrato switch appear on the
stationary plates and are picked up, one at a time, by the rotor. Connection to the
rotor is made by carbon brushes, as shown in figure 5, Index A of the Vibrato and
Percussion section. Two brushes touch the sides of the contact pin and a third
presses on the end, in order to eliminate the possibility of contact failure.
5~28. Figure 1 in the Vibrato and Percussion section shows the vibrato circuit.
5~29. The vibrato switch has no OFF position, and 3 vibrato chorus positions (Cl,
C2, and C3) are included in it as well as the 3 vibrato positions (VI, V2, and V3).
The vibrato effect is turned ON and OFF for each manual separately by means of
VIBRATO SWELL and VIBRATO GREAT tablets on the manual assembly.
5-30. The preamplifier used with this circuit has two separate channels into which
signals from the VIBRATO GREAT and VIBRATO SWELL tablets are fed. (Reference
paragraph 5—37. ) The VIBRATO signal goes through a preliminary amplifier, through
the vibrato system, and then into additional stages of amplification. The NO VIBRATO
signal also has a preliminary amplifier, but bypasses the vibrato system and goes
directly into the additional amplifier stages.
19
5-31. MANUAL CHASSIS ASSEMBLY.
5~32. The 9 contact springs on each key are connected by resistance wires to the
proper terminals on the terminal strip and carry the harmonics of the particular
note with which they are associated. The resistance wires avoid overloading of the
generators and thus allow each generator to be used independently to feed a number
of key circuits. All key contacts are alive at all times. When a playing key is
depressed, its 9 frequencies are impressed on the 9 bus bars of the manual. No wires
are connected to these bus bars; a preset or adjust key must be depressed to
complete the circuit. (See console schematic) Each preset or adjust key is provided
with 9 contacts identical to those on the playing keys and is further provided with
a locking and tripping mechanism, the purpose of which is to permit only 1 preset or
adjust key to be in operation at a time. The cancel key releases a depressed preset
or adjust key; this cancel key has no contacts.
5—33. Flexible wires connect the 9 contacts of each adjust key (A# and B) to the 9
drawbars controlled by the key. The wires are color-coded for identification. Each
drawbar makes contact (according to the stop position to which it is drawn) with any
one of 9 busbars connected to taps on the mixing transformer. (See console
schematic). The bus bars correspond to different intensities of sound.
5~34. The 9 preset keys ( C# to A ) are connected by flexible leads to the preset
panel in the back of the console. (See Rear Views of consoles at end of General
Descriptions section). The preset panel consists of 2 sets of 9 busbars which
correspond to those in the drawbar assembly and which are connected to the same taps
on the matching transformers.
5—35. The matching transformers are mounted on the manual chassis assembly as shown
in Rear Views of consoles at end of the General Descriptions section. Shielded leads
carry the signals from the secondaries of these transformers to the preamplifier.
5—36. PEDAL SWITCH ASSEMBLY. The pedal switch assembly is similar in operation to
the manual chassis assembly (reference paragraphs 5—3 1 to 5—35 inclusive) ; the pedal
switch assembly, however, contains only 4 bus bars instead of 9. A flat spring at
the end of each pedal of the detachable pedal clavier depresses a small plunger, as
shown in figure 5, (p. 6) of the Manuals, Pedals, etc. section, on the pedal switch
assembly and actuates a double set of contact springs, thus making eight contacts
available for each note the pedal contact springs are connected by decoupling
resistance wires to terminals. A cable connects these terminals through a wiring
tube to the proper terminals on the main tone generator strip. The pedal switch bus
bars are connected, by means of four colored wires, through a filter reactor
and resistor network to the pedal drawbars. (See figure 5-9 on next page. ) The
reactor and resistors filter out undesirable higher harmonics and serve to balance
the pedal tones.
20
TERMINALS
INSULATING
BUS BAR
SEPARATOR
PEDAL
SWITCH PUSHER
^RESISTANCE
WIRES
SWITCH
CONTACT
Figure 5—9. Pedal Switch Contacts
5-37. VOLUME CONTROL AND PREAMPLIFIER ASSEMBLY.
5~38. Typical Circuit Before Pre-amplifier.
5~39. Each voltage of predetermined frequency produced by the tone generator is
connected to one or more key contacts. When the associated playing key is depressed,
this voltage is impressed upon the bus bar and is carried through the preset key
switch to the preset panel. The voltage is then fed to one of the several taps of the
matching transformer which is associated with the manual being played. From the high
impedance secondary of the matching transformer, this voltage (combined with others
which may be fed through simultaneously) passes to one of the preamplifier input
circuits. (Vibrato ON or OFF circuit).
5~40. Power to operate the preamplifier and power amplifier is supplied through the
run switch circuit as shown in the console schematic.
5-41. Preamplifier Circuit, Input.
5~42. The signal from each mixing transformer is sent to the Vibrato ON-OFF tablet
associated with its particular manual, and is then carried to the VIBRATO or NO
VIBRATO preamplifier input, depending on the position of the tablet.
5-43. The input circuits are similar, with one extra stage of amplification in the
VIBRATO channel to compensate for the loss that occurs through the phase shift
network and associated scanner. The input tube V4 receives the signals from VIBRATO
and NO VIBRATO circuits and further amplifies them. The signal then is impressed on
the FOUD stator of the volume control, and on the SOFT stator through a compensating
network.
21
5-44. Volume or Swell Control.
5~45. The volume control is activated by the swell pedal connected by an appropriate
linkage. (See Rear View of consoles in General Descriptions section) The volume
control assembly consists of two sets of stator plates, similar to those used in the
scanner assembly. (See figure 5 in Vibrato and Percussion section. ) A rotor assembly
of similar size is moved by the swell pedal and is capable of meshing with either
stator or a portion of each. The degree of mesh determines the strength of the
entire signal.
5~46. The signal is further amplified by the second section of V4 and sent to driver
tube V3 which in turn drives the 12BH7 output tube.
5~47. PERCUSSION SYSTEM. (See console schematic).
5~48. The Touch Response percussion feature is controlled by four tilting tablets
(figure 8 in General Descriptions section). It is available only on the upper manual
and only when the B adjust key is depressed. Percussion tones are produced by
borrowing the second or third harmonic (depending on position of the Percussion
Harmonic Selector tablet) from the corresponding drawbar of the upper manual B adjust
key group, amplifying it, returning part of it to the same drawbar, and conducting
the balance through push-pull control tubes which, when keyed, cause the signal
to fade away at a pre-determined rate.
5~49. With the percussion tablet on, B adjust key pressed, and an upper manual
playing key pressed, the second or third harmonic signal goes to percussion input
terminal H on the preamplifier chassis and is amplified by T4 and T5.
The percussion input transformer T5 not only provides push-pull signal for the
control tube V7 but also has a third winding which feeds signal back to the 2nd or
3rd harmonic drawbar through equivalent key circuit resistor R50
and terminal J.
5-50. When a key is depressed, the note first sounds loudly, after passing through
the control tube V7, transformer T6, a high pass filter, and terminal D to the grid
of V4. Immediately, capacitor C31 in the control tube grid circuit begins to
discharge, causing the signal to fade away.
5~51. This circuit works as follows: Terminal K (Approximately -25 volts) is
connected to the 8th harmonic B adjust key drawbar wire, which is connected through
the adjust key contact to the manual busbar. Pressing any upper manual key connects
this busbar to a tone generator terminal and virtually grounds terminal K through the
tone generator filters. This virtually grounds the plate of V6, stops conduction,
isolates the cathode of V6, and thus isolates the grid circuit of control tube V7.
The grid then drifts from about -25 volts to about -15 volts, at a rate determined by
the time required for C31 to discharge through R57 and R58. At the completion of this
sequence, the percussion signal is blocked so that it is no longer audible.
22
5~52. No further percussion signal can be heard until all keys of the upper manual
are released so that the control tube V7 grids can again drop to -25 volts (the rate
of this drop is fixed by the time required to charge C31 to -15 volts through R55 and
R56) . Thus the percussion effect is heard only when keys are played in a detached
manner; that is, when all keys are released before pressing the next one.
5—53. REVERBERATION UNIT. (See figure 3 in the Reverberation section) This device
simulates musically desirable echoes in a large room. An electrical signal
from the amplifier is applied to the driver coil in the reverberation unit, which
converts the electrical signal into a twisting movement of 3 coil springs. This
motion is transmitted along each spring to a pickup unit, where part of it is
converted back to electrical energy. The remaining portion is reflected back
to the driver and again back to the pickup after a time interval determined by the
spring length. This reflection process continues until the signal level is reduced to
about one millionth of its signal value so that it is no longer audible. The springs
are different in length and thus there are 3 separate sets of echoes, each repeated a
number of times. Electronic amplification circuitry associated with the reverberation
unit is contained in the power amplifier, described below.
5~54. POWER AMPLIFIER. (See figure 26 in Tone Cabinet Amp section of Wiring and
Schematic Diagrams )
5—55. This is a 3-channel amplifier with 2 treble channels (one for non-reverberated
and one for reverberated signal) and a bass channel, with a cross-over point of 200
cycles. Each channel has two 6BQ5 output tubes with self bias. Each treble channel
drives a 12 " speaker, and the bass channel drives two 15 " speakers in parallel.
5~56. The power supply unit is a separate chassis housing the power transformer,
rectifier tubes, filter, and input connections for power and signal. A 6-pin plug
engages the console cable, and a 5-pin receptacle is provided for plugging in
additional tone cabinets. The console cable consists of 5 conductors; 2 for AC power,
2 for push-pull signal, and ground.
5~57. The push-pull signal from the console (G1 and G2) drives treble input tube VI.
Resistance capacitance filters ahead of VI filter out signal frequencies below 200
cycles. VI drives output tubes V2 and V3 of the treble direct channel. It also drives
double triode tube V9 which, in turn, drives the reverberation unit.
5~58. The output of the reverberation unit passes through transistor TR-1, and part
of the signal goes to the treble reverberation switch. This adjusts the amount of
reverberated signal going into V10, which drives output tubes Vll and V12 of the
treble reverberation channel. The switch, in its off position, picks up signal from
input terminal Gl, in order to make use of the channel for non-reverberated signal
when the treble reverberation is off.
5~59. Both treble channel output transformers have tertiary windings which supply
inverse feedback signal to the cathodes of the output tubes.
23
5~60. A portion of the output of transistor TR-1 goes to double triode tube V4, which
is connected as a phase splitter to drive the push-pull bass channel. The output of
V4 goes to the bass reverberation switch, which is also connected to the input
terminals G1 and G2. The bass channel receives a large amount of reverberated signal
along with some direct signal in the HI position, only non-reverberated signal in the
OFF position, and varying mixtures in the intermediate positions.
5~61. A filter network following the bass reverberation switch filters out signal
frequencies above 200 cycles. Following it is a room size switch which can be used to
provide better balance by reducing the bass volume when used in a small room. The
signal then feeds push-pull tubes V5 and V6, which drive the bass output tubes V7 and
V8.
5-62. REPLACEMENT OF COMPONENTS
5-63. TONE GENERATOR ASSEMBLY
5~64. Remove the four hexagonal-head bolts and their associated springs and T-washers
which secure the generator assembly to the console.
5~65. Remove the four screws from the left and right hand side panels of the music
rack. Tilt the bottom of the music rack by lifting the side panels, and remove the
rack by pulling outward.
5~66. Remove the 4 chassis bolts (underneath the console) and the 2 machine screws
(under the front lower manual rail) that hold the entire manual chassis in place.
5~67. Disconnect the 79 manual leads, 68 pedal leads, 4 ground wires, and the pedal
filter leads. The pedal filter is located on the rear surface of the upper manual
assembly.
5~68. Pull out all drawbars to position 8, and then tilt the manual chassis from the
front as far as the top of the console will permit. Place suitable wedges or blocks
on both sides of the manual chassis to hold it in this position. The manual chassis
must be tilted to provide adequate clearance for the bolts in the comers of the main
generator assembly.
5~69. Unhook the four suspension springs on which the generator assembly rides.
5~70. Lift up the generator assembly and remove it at the rear of the console.
5~71. Install a replacement generator assembly by reversing the procedure given above
for removing it.
5~72. MIXING TRANSFORMER ASSEMBLY. The Assembly of two mixing transformers is
provided complete with all leads to the preset panels, and can be removed as follows:
a. Remove the rear panel.
b. Remove the two screws which secure the transformer cover in place.
c. Label and disconnect all leads from the mixing transformers where they
connect to the preset panels.
d. Unsolder green and yellow shielded wires at mixing transformers.
e. Remove the two wood screws which secure the mixing transformer assembly to
the manual chassis block.
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f. Secure the replacement mixing transformer assembly in place by reversing the
procedures given above.
5-73. PLAYING KEY.
5~74. Replacement of playing key on upper manual will be accomplished as follows:
a. Remove the four screws from the left and right-hand side panels of music
rack. Tilt the bottom of the rack by lifting the side panels and then remove the rack
by pulling outward.
b. Remove the 2 wood screws and the 2 overhead bolts from the ends of the
drawbar base.
c. Lift and block up the entire drawbar base.
d. To remove a black key, loosen its key mounting screw, unhook key from screw,
and lift out key.
e. To remove a white key, loosen its key mounting screw and those of adjacent
black keys. Unhook these keys from screws, push them back, and lift out white key.
f. Insert a replacement key and install by reversing the directions given above
for removal.
g. Adjust the tension of the replacement playing key by comparison with the
adjoining key.
5-75. Replacement of playing key on lower manual will be accomplished as follows:
a. Remove the four screws from the left and right hand side panels of the music
rack. Tilt the bottom of the rack by lifting the side panels and then remove the rack
by pulling outward.
b. Remove the two oval-head bolts from the ends of the stop base.
c. Pull out all drawbars to position 8.
d. Tilt the upper manual as far back as the top of the console will allow, and
then wedge or block it in this position.
e. Complete the replacement of the playing key on the lower manual by following
the same procedure given above for upper manual keys.
5-76. PEDAL SWITCH ASSEMBLY.
5-77. Replacement of pedal switch assembly will be accomplished as follows:
a. Remove the pedal clavier by lifting it up in front and then pulling straight
back.
CAUTION:
Be careful to prevent damage to the delicately
constructed pusher levers (switch
pushers) at the end of each pedal.
b. Unsolder the pedal cable wires from terminals on the generator.
c. Disconnect the brown and black leads from the filter located on the rear
surface of the upper manual assembly.
d. Disconnect the orange, red, and yellow pedal signal leads from the resistor
strip on the rear surface of the upper manual assembly.
25
e. Use small wooden blocks to raise and support the entire console a few inches
off the floor to provide the necessary clearance for the removal of the pedal switch
assembly.
f. Loosen and remove the screws which hold the wiring tube (through which the
pedal wiring cable passes to the tone generator) to the console shelf, the 3
oval-head and 1 hexagonal head screws which hold the pedal switch in place, and the
screw which holds the swell pedal rod in place.
g. Lift the cover board and remove the screws which hold the pedal switch
assembly to the back rail of the console.
h. Loosen the large bolt at each end of the pedal switch assembly then remove
the nuts attached to these bolts. Drop the assembly carefully and remove it.
i. Install a replacement pedal switch assembly in place by reversing the
procedures above.
5-78. MANUAL CHASSIS.
5-79. Replacement of manual chassis will be accomplished as follows:
a. Remove the rear panel of the console.
b. Remove the four screws on the left and right hand side panels of the music
rack.
c. Lift the side panels to tilt the bottom of the rack, and then remove the
rack by pulling outward.
d. Remove the 4 chassis bolts (under the console) and the 2 machine screws
(under the front lower rail) that secure the entire manual chassis in place.
e. Disconnect all preamplifier leads.
f. Loosen set screw in expression control lever arm and detach arm from
preamplifier.
g. Remove preamplifier from shelf after taking
out mounting screws.
h. Unsolder (do not cut) the 79 manual leads, 2 ground leads, 3 pedal signal
leads (red, orange, and yellow), and the pedal filter leads (brown and black).
i. At the power terminal panel, unsolder the five wires leading to the manual
chassis start and run-motor switches. Determine these leads by tracing the leads from
the switches.
j. Detach pilot lamp bracket by removing two wood screws.
k. Unsolder eight scanner wires from terminals on back of drawbar base.
l. Unsolder brown wire from vibrato line.
m. Tie the disconnected cables to the chassis to prevent damage to the other
console components when the manual chassis is removed.
n. Remove the manual chassis through the rear of the console. Slide the chassis
out carefully. Because of frame construction, the chassis will drop suddenly before
it is entirely out of the console. Two men are required to remove the manual chassis
from the console.
o. Install a replacement chassis by reversing the procedure above. (See figure
10 in the Cables and Connections section ).
5-80. SWITCHES FOR START AND RUN MOTORS.
26
5~81. The switches for the start and run motors are both mounted on the same metal
plate; the following replacement instructions are equally applicable to each:
a. Remove the black bakelite switch handle by unscrewing it in a counter
clockwise direction.
b. Remove the round knurled nut which holds the switch to the metal plate.
c. Remove the four oval-head screws which hold the switch plate to the music
rack.
d. Remove the rear panel of the console.
e. Unsolder the leads (from the defective switch) at the power terminal panel
on the generator. One lead (black) is wired to the start switch. Four leads, 1
yellow, 1 black, 1 blue, and 1 brown, are wired to the run switch. (See Console
schematic). Unscrew or unsolder jumper wire between switches.
f. Remove the tape which secures the wires together. Unbraid the wires
connected to the defective switch up to the manual chassis so that the switch can be
removed.
g. Pull out the switch. Note the position of the switch with respect to the
color of the wires so that the replacement switch will be installed in the correct
position.
h. Install the new switch in the proper position. Braid and tape the wires
carefully so that they will not interfere with the operation of the generator run
motor.
i. Solder the leads of the replacement switch to the power terminal panel.
j. Operate the switch to determine that it has been installed properly.
k. Replace the rear panel.
5~82. START MOTOR (See figure 5~3 on p. 17 of this section).
5~83. Replacement of the start motor will be accomplished as follows:
a. To make the start motor accessible, follow the procedure for removing the
main tone generator. (Reference paragraph 5—63. )
b. Remove start motor capillary threads from oiling trough.
c. Disconnect the leads to the start motor at the power terminal panel on the
generator.
d. Using a socket wrench, remove the two start motor mounting screws.
e. Secure a replacement start motor in position by reversing the procedures
above.
5-84. RUN MOTOR AND VIBRATO SCANNER ASSEMBLY.
5~85. Replacement of run motor and vibrato scanner assembly will be accomplished as
follows :
a. Remove the rear panel.
b. At the power terminal panel on the generator, unsolder the red and black
wires which lead to the run motor that is to be replaced. (See console wiring
diagram. )
c. Unsolder 7 scanner wires from terminals on back of stop base and 2 scanner
wires from line box.
d. Remove shielded lead attached to SCAN at preamplifier.
e. The running motor is secured by four machine screws to the generator frame.
Remove the nuts and lock washers, and then disengage the flywheel coupling springs.
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f. Remove the entire motor and scanner assembly by means of a gentle pull.
g. Secure a replacement motor and vibrato scanner assembly in place by
reversing the procedures above.
SCANNER REMOVAL. DISASSEMBLY AND REPAIR PROCEDURE
1. Detach motor and scanner assembly (A) from the generator assembly by removing four
(4) nuts from the synchronous motor which anchors the motor to the "L" brackets of
the generator assembly.
2. Remove the cable connections in the organ so motor and scanner assembly is free
from organ.
3. Note A. C. , line box, and output connections for reassembly.
4. Locate oil cup (B) and oil felt (C) inside cup. The oil felt must be removed and
the cotton threads unwrapped from the felt before separating the scanner and motor.
Remove felt retainer spring (D) and lift up on the felt to remove the threads. (Do
this very carefully to avoid breaking the cotton threads). After removing the threads
from the oil felt take a pick or a paper clip and remove the three threads from the
one side of the oil cup by pulling them through the hole in the cup. The thread from
the other side of the cup need not be removed.
5. Locate screws (E) which hold the motor and scanner assembly together. Remove the
screws and pull the motor and scanner assembly apart. Note: There is a gear on the
end of the motor shaft and must be guided through the hole of the scanner housing to
separate the motor and scanner.
6. Remove two screws (F) from the rear cover (G) of the scanner. Before removing the
cover note that there is a shielded wire attached to the cover. This wire is
connected inside the scanner and there is very little slack in the wire. Remove the
cover and tip it back carefully so you can see inside. Locate the carbon brush audio
pick-up assembly (J) . The carbon brushes must be removed before the main housing
assembly cover (M) is removed, in order to prevent damage to the carbon brushes and
tension springs. Lift end brush (I) and slip the two carbon brushes (H) off the rotor
contact pin. (Be extremely careful of the rotor contact pin during disassembly so
that you do not bend or break the pin) .
28
Should it be necessary to remove the carbon brush audio pick-up assembly (J) ,
desolder the audio wire from the brush assembly and remove the two (2) screws (K) . To
remove the end brush (I) remove screw (L) and separate from the brush assembly.
7. Remove the four (4) screws (N) and slip the housing cover (M) off the main
assembly. Note: Mark the housing cover (M) and the main assembly chassis (U) to
indicate the starting point of the scanner cable, also mark the location of the cable
clip (0).
8. Stationary plates (P) and rotor (Q) are mounted on the main assembly chassis (U) .
Remove two (2) of the stationary plates (P) , by removing screws (R) . When removing
the stationary plates from the assembly you will notice that there are insulator (S)
and (T) on both sides of the main assembly chassis, insulating the stationary plates
from the assembly (U) . Then remove the rotor assembly (Q) by loosening the two (2)
Bristol type set screws (V), to avoid damaging the rotor contact pin during
disassembly.
29
9. Remove the remaining (14) stationary plates and insulators.
10. Clean the stationary plates, rotor plates and other metal parts using a reon
spray or other cleaning solvents that do not leave any residue after drying. An
absorbent cloth or swab can be used in conjunction with the cleaner.
11. Spray metal coated parts with a clear lacquer. Caution: Do not allow spray to get
on oil threads or rotor pick-up pin.
12. In most scanner repair you need not go further in disassembly than step number
eleven (11) but should conditions warrant further disassembly continue with number
thirteen (13), otherwise install new insulators and reassemble the scanner.
13. In removing the gear housing assembly (ff) there are four (4) screws (X) holding
the assembly on to the main assembly chassis (U) . Upon removing the gear housing
assembly you will notice the Bakelite gear and shaft assembly (Y) . The springs on
either side of the Bakelite gear also intermeshes with the metal gear of the
synchronous motor to drive the scanner.
14. To reassemble the scanner reverse this procedure.
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5-86. TONE GENERATOR FILTERS.
5~87. Filters used for frequencies numbered 49 to 91 inclusive, as referenced in
paragraphs 5-9 to 5—1 1 inclusive, are resonant reactor capacitor units, and will be
replaced as follows:
a. Unsolder all leads.
b. Remove the two screws holding the filter.
c. Remove the component.
d. Replace the component by reversing the procedures above.
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